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Rutherford’s Model of an Atom

We know a structure of an atom consists of electrons, protons, and neutrons . This was accurately presented after several scientists came up with different models. The classic model of an atom was given by Ernest Rutherford called the Rutherford atomic model or Rutherford model of the atom. However, it is not considered the accurate representation of an atom anymore. Let us know more about this model.

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Rutherford atomic model.

Rutherford proposed that an atom is composed of empty space mostly with electrons orbiting in a set , predictable paths around fixed, positively charged nucleus .

Rutherford's Model of an Atom

Rutherford’s Atomic Model (Source Credit: Britannica)

The concept of atom dates back to 400 BCE when Greek philosopher Democritus first conceived the idea. However, it was not until 1803 John Dalton proposed again the idea of the atom. But at that point of time, atoms were considered indivisible. This idea of an atom as indivisible particles continued until the year 1897 when British Physicist J.J. Thomson discovered negatively charged particles which were later named electrons.

To understand this concept in more detail you should read the Structure of Atom

He proposed a model on the basis of that where he explained electrons were embedded uniformly in a positively charged matrix. The model was named plum pudding model. However, J.J. Thomson’s plum pudding model had some limitations. It failed to explain certain experimental results related to the atomic structure of elements.

alpha particle scattering experiment class 11

A British Physicist “Ernest Rutherford” proposed a model of the atomic structure known as Rutherford’s Model of Atoms. He conducted an experiment where he bombarded α-particles in a thin sheet of gold. In this experiment, he studied the trajectory of the α-particles after interaction with the thin sheet of gold.

You can download  Atom Cheat Sheet by clicking on the download button below

alpha particle scattering experiment class 11

Browse more Topics under Structure Of Atom

  • Introduction: Structure of Atom
  • Atomic Number
  • Bohr’s Model of Atom
  • Charged Particles in Matter
  • Mass Number
  • Thomson’s Model of an Atom
  • How are Electrons Distributed in Different Orbits (Shells)?
  • Sub-Atomic Particles
  • Atomic Models
  • Shapes of Atomic Orbitals
  • Energies of Orbitals
  • Quantum Numbers
  • Development Leading to Bohr’s Model of Atom
  • Emission and Absorption Spectra
  • Towards Quantum Mechanical Model of Atom

Rutherford Atomic Model Experiment

In Rutherford’s experiment, he bombarded high energy streams of α-particles on a thin gold foil of 100 nm thickness. The streams of α-particles were directed from a radioactive source. He conducted the experiment to study the deflection produced in the trajectory of α-particles after interaction with the thin sheet of gold. To study the deflection, he placed a screen made up of zinc sulfide around the gold foil. The observations made by Rutherford contradicted the plum pudding model given by J.J. Thomson .

Rutherford’s Gold Foil Experiment (Source Credit: Britannica)

Observations of Rutherford Model Experiment

On the basis of the observations made during the experiment, Rutherford concluded that

  • Major space in an atom is empty – A large fraction of α-particles passed through the gold sheet without getting deflected. Therefore, the major part of an atom must be empty.
  • The positive charge in an atom is not distributed uniformly and it is concentrated in a very small volume  – Few α-particles when bombarded were deflected by the gold sheet. They were deflected minutely and at very small angles. Therefore he made the above conclusion.
  • Very few α-particles had deflected at large angles or deflected back. Moreover, very few particles had deflected at 180 o . Therefore, he concluded that the positively charged particles covered a small volume of an atom in comparison to the total volume of an atom.

What is the difference between the Thomsons and Rutherford Atomic model?

Postulates of Rutherford atomic model based on observations and conclusions

  • An atom is composed of positively charged particles. Majority of the mass of an atom was concentrated in a very small region. This region of the atom was called as the nucleus of an atom. It was found out later that the very small and dense nucleus of an atom is composed of neutrons and protons.
  • Atoms nucleus is surrounded by negatively charged particles called electrons . The electrons revolve around the nucleus in a fixed circular path at very high speed. These fixed circular paths were termed as “orbits.”
  • An atom has no net charge or they are electrically neutral because electrons are negatively charged and the densely concentrated nucleus is positively charged. A strong electrostatic force of attractions holds together the nucleus and electrons.
  • The size of the nucleus of an atom is very small in comparison to the total size of an atom.

Learn more about Thomsons Model of an Atom, by J.J. Thomsons , which was the first model of Atom.

Drawbacks of Rutherford Model

Limitations of Rutherford Atomic Model

Rutherford’s experiment was unable to explain certain things. They are:

  • Rutherford’s model was unable to explain the stability of an atom. According to Rutherford’s postulate, electrons revolve at a very high speed around a nucleus of an atom in a fixed orbit. However, Maxwell explained accelerated charged particles release electromagnetic radiations . Therefore, electrons revolving around the nucleus will release electromagnetic radiation.
  • The electromagnetic radiation will have energy from the electronic motion as a result of which the orbits will gradually shrink. Finally, the orbits will shrink and collapse in the nucleus of an atom. According to the calculations, if Maxwell’s explanation is followed Rutherford’s model will collapse with 10 -8 seconds. Therefore, Rutherford atomic model was not following Maxwell’s theory and it was unable to explain an atom’s stability.
  • Rutherford’s theory was incomplete because it did not mention anything about the arrangement of electrons in the orbit. This was one of the major drawbacks of Rutherford atomic model.

Even though the early atomic models were inaccurate and could not explain the structure of atom and experimental results properly. But it formed the basis of the quantum mechanics and helped the future development of quantum mechanics.

Solved Questions for You

Question: Name the part of an atom discovered by Rutherford α-particles scattering experiment

Answer : The answer is 4. Rutherford α-particles scattering experiment led to the discovery of nucleus.

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Rutherford’s Alpha Scattering Experiment for JEE

  • Rutherfords Alpha Scattering Experiment

ffImage

Introduction

J. J. Thomson's plum pudding model failed to explain experimental findings of atomic structure. There was still no clear model that defined atoms, so Ernest Rutherford, a British scientist, conducted an experiment in 1909 and discovered and postulated the atomic structure of elements and the Rutherford Atomic Theory Model based on his findings.

Rutherford’s Scattering Experiment

In this experiment, a piece of a radioactive substance (radium) is placed in a lead block. Only a limited beam of alpha particles might escape since the block is designed with slits. A high-energy a-particle beam was focused on a thin gold foil (thickness of about 100 nm). A moveable circular screen coated with zinc sulphide is placed around the gold foil to detect the a-particles after scattering.

When alpha particles collide with the zinc sulphide screen, light flashes or scintillations appear, which can be observed. It was feasible to determine the proportions of the a-particles that were deflected through various angles by looking at different parts of the screen.

Rutherford’s scattering experiment diagram

Rutherford’s scattering experiment diagram

Observations of Rutherford’s Alpha Scattering Experiment

Scattering of alpha particles and Rutherford’s atomic structure

Scattering of alpha particles and Rutherford’s atomic structure

1. Rutherford's observations led him to the conclusion that: “A large proportion of the α- particles that bombarded the gold sheet passed through it without deflection”. Hence, the majority of the space in an atom is empty.

2. Only a few particles deflected back (deflection angle of 180 degrees). As a result, positively charged particles in an atom occupy a small fraction of the overall volume of the atom.

3. According to Thomson's Model, if the atom's positive charge was uniformly distributed, positively charged a-particles with a significant mass (4 a.m.u.) would pass through a weak electric field mostly undeflected or slightly deflected. He did discover that several of the a-particles had significant deflections. Some particles even resurfaced from the foil. As a result, Thomson's Model was eliminated as it couldn't explain this data.

Conclusion of Rutherford’s Scattering Experiment

Rutherford explained these observations as follows:

(i) As the majority of the alpha-particles passed through the gold foil undeflected, there must be a significant amount of unoccupied space within the atom.

(ii) Alpha particles have a lot of mass and are positively charged. Due to the huge force of repulsion, they can only be deflected if they closely approach a heavy positively charged material. The presence of a heavy positively charged mass in the atom is indicated by the fact that some of the alpha particles are deflected to particular angles. Furthermore, as just a few a-particles experienced substantial deflections, this mass must be occupying a very tiny space within the atom.

(iii) The direct collision with the massive positively charged bulk was explained as the cause of the strong deflections or even bouncing back of alpha particles from the foil.

The nucleus is the positively charged heavy mass that occupies only a limited volume in an atom. It is thought to be present in the atom's nucleus.

Figure 1 depicts all these different sorts of alpha-particle deflections from atoms. The graphic shows that alpha-particles passing far away from the nucleus experience no deflections, those passing close to the nucleus experience small deflection and the few that hit the nucleus are either deflected to enormous angles or retrace their routes. Rutherford proposed a hypothesis for the structure of the atom termed Rutherford's Nuclear Model of Atom based on the above experiments and observations.

Rutherford’s Nuclear Model of Atom

Let us explain the Rutherford model of an atom. The main features of this model are:

(i) The whole mass and positive charge of an atom are concentrated in the nucleus, a very small region near the centre. When compared to the whole volume of the atom, it was discovered that the nucleus occupies a negligible amount of space.

(ii) The nucleus is surrounded by negatively charged electrons that orbit the nucleus at extremely high speeds in circular routes known as ‘orbits’.

As a result, Rutherford's atom model resembles the solar system, with the nucleus acting as the sun and circulating electrons acting as planets.

(iii) The electrostatic forces of attraction hold the electrons and nuclei together.

(iv) The majority of the space between the nucleus and the rotating electrons in an atom is vacant.

Limitations of the Rutherford Model

According to the Rutherford Model, electrons circulate the nucleus in well-defined orbits. When a body moves in an orbit, it accelerates (if its speed is constant, it must be accelerated by the change in direction). In the nuclear model, an electron is accelerating.

When charged particles are accelerated, according to Maxwell's electromagnetic theory, they should create electromagnetic radiation (it is not applicable for planets because they are uncharged). As a result, an electron in an orbit will produce radiation, which is carried by energy carried by electronic motion. As a result, the orbit will continue to shorten. (Calculations show that an electron spiralling into the nucleus should take only 10-8 seconds.)

However, this does not occur. As a result, the Rutherford model fails to explain atom stability. Electrostatic attraction between the dense nucleus and the electrons would drive the electrons toward the nucleus to produce a tiny version of Thomson's model of the atom if the electrons were deemed stationary.

Furthermore, this model reveals nothing about atoms' electronic structure, how electrons are organized around the nucleus and what energies are associated with them.

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FAQs on Rutherford’s Alpha Scattering Experiment for JEE

1. What is the charge of an alpha particle and what is its mass?

The nuclei of some radioactive elements spontaneously release a positively charged particle. It is the same as a helium nucleus with a mass number of 4 and a positive electrostatic charge. It has short-range and low penetration power (a few centimetres in the air). Two protons and two neutrons constitute an alpha particle. As a result, whenever a nucleus emits an alpha particle, it loses two protons, decreasing its atomic number by two. They are made of heavy elements like radium, thorium, uranium and plutonium which decay radioactively.

2. How did Niels Bohr fix Rutherford's Model's flaw?

Two new notions played a vital influence throughout the development of new models to improve the Rutherford model of an atom. These are the following:

Electromagnetic radiation has a dual behavior. This implies that light possesses both particles and wave qualities. Atomic spectra are the second type of atomic spectra. The experimental facts concerning atomic spectra can be explained only by assuming quantised (fixed) electronic energy levels in atoms.

Bohr was the first to discover that electrons move about the nucleus in different orbits and that the number of electrons in the valence shell can be used to predict an element's properties.

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Chapter 1: Matter in our Surroundings

  • Matter is Made of Tiny Particles
  • Why Solids, Liquids and Gases Have Different Properties
  • Classification of Matter
  • Brownian Movement
  • States of Matter: Solid, Liquid, Gas and Plasma
  • Evaporation
  • Effects of Relative Humidity and Wind Speed
  • How Does Evaporation Cause Cooling?
  • Effect of Change of Temperature
  • Melting Point
  • What is Vaporization?
  • Condensation
  • Effects of Change of Pressure
  • Difference between Rigidity and Fluidity of Matter
  • Prove That Liquids have No fixed Shape but have a Fixed Volume
  • Diffusion in Solids, Liquids, and Gases
  • What is the Unit of Temperature?
  • What is the Relationship Between Celsius and Kelvin Scale of Temperature?
  • Liquification of Gases
  • How to demonstrate the Presence of Water Vapour in Air?
  • What is Plasma and Bose-Einstein Condensate?

Chapter 2: Is Matter Around Us Pure?

  • Solution: Properties of Solution
  • Saturated and Unsaturated Solutions
  • Concentration of a Solution
  • Suspensions
  • How will you distinguish a Colloid from a Solution?
  • Classification of Colloids
  • Tyndall Effect
  • Separation of Mixtures
  • How to separate a Mixture of Two Solids?
  • Separation by a suitable solvent
  • Separation of Mixtures using Sublimation and Magnets
  • How to Separate a Mixture of a Solid and a Liquid?
  • Filtration: Definition, Process, Diagram and Examples
  • Water Purification
  • Centrifugation
  • How to Separate Cream from milk?
  • Difference Between Homogeneous and Heterogeneous Mixture
  • Difference Between Compound and Mixture
  • Factors affecting Solubility
  • Separation by Evaporation
  • Crystallization
  • Chromatography
  • Distillation
  • Separation of Mixtures of Two or More Liquids
  • Fractional Distillation
  • Pure and Impure Substances
  • What is an Element?
  • Metals, Non-Metals and Metalloids
  • Properties of Metals and Non-Metals

Chapter 3: Atoms and Molecules

  • Laws of Chemical Combination
  • Law of Conservation of Mass
  • Verification of the Law of Conservation of Mass in a Chemical Reaction
  • Law of Constant Proportions
  • What is Atom?
  • Atomic Mass
  • How Do Atoms Exist?
  • Cations vs Anions
  • What are Ionic Compounds?
  • What are Monovalent Ions?
  • What are Divalent Ions?
  • Trivalent Ions - Cations and Anions
  • Polyatomic Ions
  • Formulas of Ionic Compounds
  • Chemical Formula of Common Compounds
  • Molecular Mass
  • Mole Concept
  • Problems Based on Mole Concepts
  • Dalton's Atomic Theory
  • Drawbacks of Dalton's Atomic Theory
  • Significance of the Symbol of Elements
  • Difference Between Molecules and Compounds
  • How to Calculate Valency of Radicals?
  • What is the Significance of the Formula of a Substance?
  • Gram Atomic and Gram Molecular Mass

Chapter 4: Structure of the Atom

  • Charged Particles in Matter
  • Thomson's Atomic Model

Rutherford Atomic Model

  • Drawbacks of Rutherford's Atomic Model
  • Bohr's Model of an Atom
  • Valence Electrons
  • Mass Number
  • Relation Between Mass Number and Atomic Number
  • Why do all the Isotopes of an Element have similar Chemical Properties?
  • Why Isotopes have different Physical Properties?
  • What is Fractional Atomic Mass?
  • Radioactive Isotopes
  • Discovery of Electrons
  • What is a Proton?
  • Rutherford's Alpha Scattering Experiment
  • Atomic Nucleus
  • How did Neil Bohr explained the Stability of Atom?
  • Electron Configuration
  • Potassium and Calcium - Atomic Structure, Chemical Properties, Uses
  • What is meant by Chemical Combination?
  • Difference between Electrovalency and Covalency

Rutherford’s Alpha Scattering Experiment

Rutherford’s Alpha Scattering Experiment is the fundamental experiment done by Earnest Rutherford’s Alpha Scattering Experiment that gives the fundamental about the structure of the atom. Rutherford in his experiment directed high-energy streams of α-particles from a radioactive source at a thin sheet (100 nm thickness) of gold. Then the deflection of these alpha particles tells us about the structure of atoms.

In this article, we will study about constituents of atoms, Rutherford’s  Alpha Scattering Experiment,

What are Constituents of an Atom?

An atom consists of Electrons, Protons, and Neutrons are the fundamental particles or sub-atomic particles that build the structure of an atom. Let us understand each term.

  • Electron: In 1897, J. J. Thomson discovered negatively charged particles towards the anode, these rays are emitted by the cathode in a cathode ray experiment. Then these negatively charged particles are proposed as Electrons .
  • Protons: In 1886, Ernest Goldstein discovered that an anode emitted positively charged particles with a different condition in the same tube,  known as Canal rays or as Protons .
  • Neutrons: A subatomic particle with no charge and a mass equivalent to protons in the nucleus of all atoms was discovered by J. Chadwick. These neutrally charged particles are termed Neutrons .

The image added below shows the structure of an atom.

Learn more about, Atomic Structure

Structure-of-Atom

Structure of Atom

Isotopes are the elements that have the same atomic number but different mass. e.g. Isotopes of the Hydrogen atoms are Protium ( 1 H 1 ), Deuterium ( 2 H 1 ) and Tritium( 3 H 1 ). Isotopes of the Carbon atoms are 12 C 6 , 13 C 6 , 14 C 6 .

Isobars are the elements that have different atomic number but have same mass number. e.g. 19 K 40 , 18 Ar 40 , 20 Ca 40 , here all the elements having same mass number hence they are isobars.

He conduct an experiment by bombarding alpha particles into a thin sheet of gold and then notices their interaction with the gold foil and trajectory or path followed by these particles.

Rutherford's Alpha Scattering Experiment

In the experiment, Rutherford passes very high streams of alpha-particles from a radioactive source i.e. alpha-particle emitter, at a thin sheet of100 nm thickness of gold. In order to examine the deflection produced by the alpha particles, he placed a screen of fluorescent zinc sulphide around the thin gold foil. Rutherford made certain observations that oppose Thomson’s atomic model.

Observations of Rutherford’s Alpha Scattering Experiment

The observations of Rutherford’s Alpha Scattering Experiment are:

  • First, he observe that most of the α-particles that are bombarded towards the gold sheet pass away the foil without any deflection, and hence it shows most of the space is empty.
  • Out of all, some of the α-particles were deflected through the gold sheet by very small angles, and hence it shows the positive charge in an atom is non-uniformly distributed. The positive charge is concentrated in a very small volume in an atom.
  • Very few of the alpha-particles(1-2%) were deflected back, i.e. only a very less amount of α-particles had nearly 180° angle of deflection. this shows that the volume occupied by the positively charged particles is very small as compared to the total volume of an atom.

Rutherford proposed the atomic structure of elements, on the basis of his experiment. According to Rutherford’s atomic model:

  • Positively charged particle was concentrated in an extremely small volume and most of the mass of an atom was also in that volume. He called this a nucleus of an atom.
  • Rutherford proposed that there is negatively charged electrons around the nucleus of an atom. the electron surrounding the nucleus revolves around it in a circular path with very high speed. He named orbits to these circular paths.
  • Nucleus being a densely concentrated mass of positively charged particles and electrons being negatively charged are held together by a strong force of attraction called electrostatic forces of attraction.

Learn about, Rutherford Atomic Model

Limitations of Rutherford Atomic Model

The Rutherford atomic model is failed to explain certain things.

  • According to Maxwell, an electron revolving around the nucleus should emit electromagnetic radiation due to accelerated charged particles emit electromagnetic radiation. but Rutherford model says that the electrons revolve around the nucleus in fixed paths called orbits. The radiation would carry energy from the motion which led to the shrinking of orbit. Ultimately electrons would collapse inside the nucleus.
  • As per the Rutherford model, calculations have shown that an electron would collapse in the nucleus in less than 10 -8 seconds. So Rutherford model has created a high contradiction with Maxwell’s theory and Rutherford later could not explain the stability of an atom.
  • Rutherford also did not describe the arrangement of electrons in the orbit as one of the other drawbacks of his model.

Regardless of seeing the early atomic models were inaccurate and failed to explain certain experimental results, they were the base for future developments in the world of quantum mechanics.

Sample Questions on Rutherford’s Alpha Scattering Experiment

Some sample questions on Rutherford’s Alpha Scattering Experiment is,

Q1: Represent Element ‘X’ which contains 15 electrons and 16 neutrons.

Atomic number of element = No. of electron = 15 Mass number of element = no. of electrons + no. of neutrons = 15 + 16 = 31 Correct representation of element X is 31 X 15 .

Q2: Name particle and give its location in the atom which has no charge and has a mass nearly equal to that of a proton.

The particle which has no charge and has a mass nearly equal to that of a proton is a neutron and it is present in the nucleus of the atom.

Q3: An atom has both electron attribute negative charge and protons attribute positive charge but why there is no charge?

Positive and negative charges of protons and electrons are equal in magnitude, they cancel the effect of each other. So, the atom as a whole is electrically neutral.

Q4: What is Valency of Sodium Atom (Na)?

The atomic number of sodium = 11. Electronic configuration (2, 8, 1). By losing one electron it gains stability hence its valency is 1.

Q5: Which property do the following pairs show? 209 X 84 and 210 X 84

Atomic number of X is the same hence the pair shows an isotopic property. So, 209 X 84 and 210 X 84 are isotopes.
Dalton’s Atomic Theory Thomson’s Atomic Model Quantum Numbers

Rutherford’s Alpha Scattering Experiment FAQs

What is name of atom which has one electron, one proton and no neutron.

Atom with one electron, one proton and no neutron is Hydrogen, ( 1 H 1 ).

What is Ground State of an Atom?

It is the state of an atom where all the electrons in the atom are in their lowest energy state or levels is called the ground state.

What was Rutherford’s Alpha Particle Scattering Experiment?

Rutherford’s Alpha Particle Scattering Experiment is the fundamental experiment that gives the basic structure of an atom.

What was Conclusion of Rutherford’s Alpha Scattering Experiment?

Conclusion of Rutherford’s Alpha Scattering Experiment is, Atom is largely empty and has a heavy positive-charged body at the center called the nucleus. The central nucleus is positively charged and the negatively-charged electrons revolve around the nucleus.

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Rutherford’s Model of an Atom

Last Updated on July 3, 2023 By Mrs Shilpi Nagpal

​Thomson’s model of atom

J.J. Thomson model

J.J. Thomson in 1904 , proposed that an atom was a sphere of positive electricity in which were embedded number of electrons. The stability of the atom was explained as a result of the balance between the repulsive forces between the electrons and their attraction towards the centre of the positive Sphere.This model is compared with a watermelon in which seeds are embedded or with a cake or pudding in which raisins are embedded. That is why this model is called as raisin pudding model a watermelon model.

This model could not explain the stability of the atom.

Rutherford Model of atom

Rutherford's Experiment

Rutherford in 1911, performed scattering experiment in which he bombarded thin walls of metals like gold, silver, Platinum or copper with a beam of fast moving Alpha particles. The source of Alpha particles was radium, a radioactive substance, placed in a block of lead. Slits were used to get a fine beam. The presence of Alpha particles at any point around the thin foil of gold after striking it was detected with the help of a circular zinc sulphide. The point at which an Alpha particle strikes this screen ,a flash of light is given out.

Observation

Rutherford's observation

1) Most of the Alpha particles passed through the foil without undergoing any deflection.

2) Few Alpha particles underwent deflection through small angles.

3) Very few were deflected back through an angle greater than 90°

1)Since most of the Alpha particles passed through the foil without undergoing any deflection, there must be sufficient empty space within the atom.

2)Since few alpha particles were deflected through small angles and alpha particles were positively charged particles, these could be deflected only by some positive body present within the atom. The alpha particles deflected were those which passed very close to this positive body.

3)Since some alpha particles were deflected back and alpha particles are heavy particle, these could be deflected back only when they strike some heavier body inside the atom.

4)Since the number of alpha particles deflected back is very very small, this shows that the heavy body present in an atom must be occupying a very very small volume.

The small heavy positively charged body present within the atom was called nucleus.

Rutherford Model of an atom

Rutherford's Model

(1) Nucleus is very small in size, carries positive charge and in which the entire mass of the atom is concentrated.

(2) Since electrons have negligible mass ,the mass of the atom is mainly due to protons and neutrons.

(3) Protons and neutrons must be present in the nucleus.

(4) Extranuclear part is the space around the nucleus in which the electrons were distributed.

Drawback of Rutherford’s Model of an atom

(1) Inability to explain the stability of atom

An atom consists of a small, heavy positively charged nucleus in the centre and the electrons were revolving around it. This model was compared with the solar system in which the planets were revolving around the sun and continue to move in their fixed circular paths because the force of attraction was balanced by the centrifugal force.

According to Maxwell’s electromagnetic theory, whenever a charged particle like electron is revolving in a field of force like that of the nucleus, it loses energy continuously in the form of electromagnetic radiation. This is because when a particle is revolving, it undergoes acceleration due to change in direction even if the speed remains constant. Thus, the orbit of the revolving electron will keep on becoming smaller and smaller, following a spiral path and ultimately the electron should fall into the nucleus. The atom should collapse.

Rutherford model could not explain the stability of the atom.

(2) Inability to explain the line spectra of the elements.

(3) Inability to describe distribution of electrons and energies of electrons.

Atomic number

Atomic number of an element = Total number of protons = Total number of electrons

The atomic number is represented by Z

Atomic number is also known as Proton number because the charge on the nucleus depends upon the number of protons.

Mass number  is the sum of protons and neutrons.

The mass number is represented by A.

Where A is mass number, Z is atomic number and X is the element.

Atoms of the same element having same atomic number but different mass number.

For Example:

(1) Isotopes of Hydrogen

1 H 1    1 H 2   1 H 3

(2) Isotopes of Chlorine

37 Cl      35 Cl

(3) Isotopes of Carbon

14 C    12 C    13 C

4) Isotopes of Oxygen

16 O    17 O    18 O

Atoms of different elements having different but same mass number are called isobars.

isobars

Atoms of different elements which contain the same number of neutrons are called isotones.

Isotones

Isoelectronic

The species containing the same number of electrons are called isoelectronic.

Isoelectronic species

About Mrs Shilpi Nagpal

Author of this website, Mrs. Shilpi Nagpal is MSc (Hons, Chemistry) and BSc (Hons, Chemistry) from Delhi University, B.Ed. (I. P. University) and has many years of experience in teaching. She has started this educational website with the mindset of spreading free education to everyone.

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Alpha Particle Scattering Experiment ( OCR A Level Physics )

Revision note.

Katie M

Alpha Particle Scattering Experiment

  • Evidence for the structure of the atom was discovered by Ernest Rutherford in the beginning of the 20th century from the study of α-particle scattering
  • The experimental setup consists of alpha particles fired at thin gold foil and a detector on the other side to detect how many particles deflected at different angles

Alpha particle experiment diagram, downloadable AS & A Level Physics revision notes

α-particle scattering experiment set up

  • α-particles are the nucleus of a helium atom and are positively charged

Alpha particle scattering, downloadable AS & A Level Physics revision notes

When α-particles are fired at thin gold foil, most of them go straight through but a small number bounce straight back

What did the Alpha Particle Scattering Experiment Show?

  • The Rutherford alpha particle scattering experiment showed that:
  • This suggested the atom is mainly empty space
  • This suggested there is a positive nucleus at the centre (since two positive charges would repel)
  • This suggested the nucleus is extremely small and this is where the mass and charge of the atom is concentrated
  • It was therefore concluded that atoms consist of small dense positively charged nuclei
  • Since atoms were known to be neutral, the negative electrons were thought to be on a positive sphere of charge (plum pudding model) before the nucleus was theorised
  • Now it is known that the negative electrons are orbiting the nucleus. Collectively, these make up the atom

Worked example

WE - Rutherford scattering question image 1, downloadable AS & A Level Physics revision notes

     ANSWER:    A

  • The Rutherford scattering experiment directed parallel beams of α-particles at gold foil
  • Most of the α-particles went straight through the foil
  • The largest value of n will therefore be at small angles
  • Some of the α-particles were deflected through small angles
  • n drops quickly with increasing angle of deflection θ
  • These observations fit with graph A

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Drawbacks of Rutherford's Atomic Model Experiment

Last updated at April 16, 2024 by Teachoo

Rutherford suggested that:

  • Electrons revolve around the nucleus in a circular path.
  • This is not possible because, if a particle follows a circular orbit, it will undergo acceleration (due to change in velocity as a result of continuous change in direction in a circular path).

8.  velocity has constant-Teachoo-01.png

  • During acceleration, charged particles radiate and lose energy.
  • After losing all energy, the charged electron will ultimately fall into the nucleus.
  • This would make the atom very unstable.
  • But we know that atoms are actually stable.
  • Hence, there was a flaw in Rutherford's model of an atom.

9. drawbacks of rutherford model-Teachoo-01.png

In text Question - Page 49 Q2, Q4

NCERT Back Exercise - Q3, Q15

Since Rutherford was unable to explain the drawbacks of his model,

Bohr came up with his model of atom.

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What are the results of alpha-particle scattering experiment ?

Rutherford's alpha-particle scattering experiment: rutherford carried out a gold foil experiment where he bombarded a very thin gold foil with positively charged alpha particles. based on the alpha particles scattering experiment, rutherford has proposed the nuclear model of an atom. results of rutherford's alpha-particle scattering experiment: most of the alpha particles passed through the foil undeflected. this shows that most space inside the atom is empty. some alpha particles got deflected at different angles. this is because the positively charged nucleus repelled positively charged alpha particles. very few alpha particles bounced back after hitting the gold foil. this shows that the nucleus is very tiny and dense..

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Alpha particle scattering experiment gave totally unexpected results. Which of the following observations were made?

The graph which depicts the result of Rutherford's gold foil experiment with α - particle is

θ : Scattering angle

Y : Number of scattered α - particles detected

(Plots are schematic and not to scale)

thumbnail

IMAGES

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COMMENTS

  1. Rutherford Atomic Model Observations and Limitations In Detail

    Observations of Rutherford's Alpha Scattering Experiment. The observations made by Rutherford led him to conclude that: A major fraction of the α-particles bombarded towards the gold sheet passed through the sheet without any deflection, and hence most of the space in an atom is empty.; Some of the α-particles were deflected by the gold sheet by very small angles, and hence the positive ...

  2. Alpha-Particle Scattering and Rutherford's Nuclear Model of Atom

    Browse more Topics under Atoms. Atomic Spectra; Bohr Model of the Hydrogen Atom; The Alpha Particle Scattering Experiment. They took a thin gold foil having a thickness of 2.1×10-7 m and placed it in the centre of a rotatable detector made of zinc sulfide and a microscope. Then, they directed a beam of 5.5MeV alpha particles emitted from a radioactive source at the foil.

  3. Rutherford Scattering

    Simulate the famous experiment in which he disproved the Plum Pudding model of the atom by observing alpha particles bouncing off atoms and determining that they must have a small core. How did Rutherford figure out the structure of the atom without being able to see it? Simulate the famous experiment in which he disproved the Plum Pudding ...

  4. Explain Rutherford's alpha-ray scattering experiment with a ...

    Conclusion of Rutherford's scattering experiment: 1. Most of the space inside the atom is empty because most of the α -particles passed through the gold foil without getting deflected. 2. Very few particles were deflected from their path, indicating that the positive charge of the atom occupies very little space. 3.

  5. Rutherford Atomic Model

    Rutherford's model of an atom stated that: There is a positively charged centre in an atom called the nucleus . Nearly all the mass of an atom resides in the nucleus . The electrons (negatively charged particles) revolve around the nucleus in circular paths. The size of the nucleus is very small as compared to the size of the atom .

  6. The Rutherford-Geiger-Marsden Experiment

    The experiments were performed between 1908 and 1913 by Hans Geiger and Ernest Marsden under the direction of Ernest Rutherford at the Physical Laboratories of the University of Manchester. In the experiment, Rutherford sent a beam of alpha particles (helium nuclei) emitted from a radioactive source against a thin gold foil (the thickness of ...

  7. Rutherford scattering experiments

    A replica of an apparatus used by Geiger and Marsden to measure alpha particle scattering in a 1913 experiment. The Rutherford scattering experiments were a landmark series of experiments by which scientists learned that every atom has a nucleus where all of its positive charge and most of its mass is concentrated. They deduced this after measuring how an alpha particle beam is scattered when ...

  8. Rutherford Scattering Experiment and Atomic Model for JEE

    Class 11 JEE Course (2023-25) Class 12 JEE Course (2023-24) JEE Repeater Course (2023-24) Class 8 JEE Foundation Course. ... Rutherford's alpha-particle scattering experiment was a successful attempt to present an atomic model. In the experiment, Rutherford used an alpha particle emitter, gold foil, and a movable fluorescent screen proper ...

  9. Rutherford's gold foil experiment (video)

    Well, that is quite an interesting question. You see, the detector the speaker speaks about here is actually a film of Zinc Sulphide positioned around the gold foil, with a small space to let the alpha particles, as mentioned by the speaker. Now, the Zinc Sulphide screen has fluorescent properties, i.e., when the scattered alpha particles hit the Zinc Sulphide screen, the points where they hit ...

  10. Rutherford's Model of an Atom

    Rutherford Atomic Model Experiment. In Rutherford's experiment, he bombarded high energy streams of α-particles on a thin gold foil of 100 nm thickness. The streams of α-particles were directed from a radioactive source. He conducted the experiment to study the deflection produced in the trajectory of α-particles after interaction with the ...

  11. Rutherford scattering

    Figure 1. In a cloud chamber, a 5.3 MeV alpha particle track from a lead-210 pin source near point 1 undergoes Rutherford scattering near point 2, deflecting by an angle of about 30°. It scatters once again near point 3, and finally comes to rest in the gas. The target nucleus in the chamber gas could have been a nitrogen, oxygen, carbon, or hydrogen nucleus.

  12. Explain Rutherford's \\[\\alpha \\] ray scattering experiment with a

    These particles are a form of radiation. Complete step by step answer: Diagram of Rutherford's \ [\alpha \] rays scattering experiment. Rutherford used the observations of Thomson's experiment to propose the atomic structure. Rutherford conducted the experiment using radioactivity phenomenon. He used radium bromide, $ {\text {RaBr}}$ which ...

  13. Rutherford's Alpha Particle Scattering Experiment

    In his alpha particle scattering (gold foil) experiment, Rutherford used alpha particles along with a zinc sulphide covered screen. The alpha particles were fired as a beam of 5.5MeV against a very thin gold foil sheet with 2.1 × 10-7 m thickness. It was assumed that all of the alpha particles would travel through the gold foil without being ...

  14. Rutherford's Alpha Scattering Experiment for JEE

    Observations of Rutherford's Alpha Scattering Experiment. Scattering of alpha particles and Rutherford's atomic structure. 1. Rutherford's observations led him to the conclusion that: "A large proportion of the α-particles that bombarded the gold sheet passed through it without deflection". Hence, the majority of the space in an atom ...

  15. Rutherford's Alpha Scattering Experiment

    Rutherford Atomic Model. Rutherford proposed the atomic structure of elements, on the basis of his experiment. According to Rutherford's atomic model: Positively charged particle was concentrated in an extremely small volume and most of the mass of an atom was also in that volume. He called this a nucleus of an atom.

  16. Alpha-particle Scattering Experiment

    Alpha-particle Scattering Experiment. Evidence for the structure of the atom was discovered by Ernest Rutherford in the beginning of the 20th century from the study of α-particle scattering. The experimental setup consists of alpha particles fired at thin gold foil and a detector on the other side to detect how many particles deflected at ...

  17. 18.3: The Geiger-Marsden Experiment

    New Mexico Tech via The New Mexico Tech Press. Figure 18.3: Schematic of Geiger-Marsden experiment. The radioactive source produces alpha particles that are collimated into a beam and directed at a gold foil. The alpha particles scatter off the foil and are detected by a flash of light when they hit the scintillation screen.

  18. Rutherford's Model of an Atom

    Rutherford Model of an atom. (1) Nucleus is very small in size, carries positive charge and in which the entire mass of the atom is concentrated. (2) Since electrons have negligible mass ,the mass of the atom is mainly due to protons and neutrons. (3) Protons and neutrons must be present in the nucleus. (4) Extranuclear part is the space around ...

  19. 6.7.1 Alpha Particle Scattering Experiment

    The Rutherford scattering experiment directed parallel beams of α-particles at gold foil. The observations were: Most of the α-particles went straight through the foil. The largest value of n will therefore be at small angles. Some of the α-particles were deflected through small angles. n drops quickly with increasing angle of deflection θ.

  20. Describe Rutherford's scattering experiment.

    List out the characters of anode rays. Describe Rutherford model of an atom. Describe the properties of cathode rays. State the conclusion drawn by Alpha ray scattering experiment of Rutherford. Q. ___ thin foil was used by Rutherford for alpha - scattering experiment. Q. In Rutherford alpha-scattering experiment, a foil of ____________ was used.

  21. Rutherford alpha particle scattering experiment ||3D Animated

    welcome to visual learningRutherford alpha particle scattering experiment ||3D Animated explanation in hinglish || Physics 12thThis channel provides educatio...

  22. Drawbacks of Rutherford's Atomic Model Experiment

    This would make the atom very unstable. But we know that atoms are actually stable. Hence, there was a flaw in Rutherford's model of an atom. Examples -. In text Question - Page 49 Q2, Q4. NCERT Back Exercise - Q3, Q15. Since Rutherford was unable to explain the drawbacks of his model, Bohr came up with his model of atom.

  23. What are the results of alpha particle scattering experiment

    Results of Rutherford's alpha-particle scattering experiment: Most of the alpha particles passed through the foil undeflected. This shows that most space inside the atom is empty. Some alpha particles got deflected at different angles. This is because the positively charged nucleus repelled positively charged alpha particles.