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
Isotopes are the elements that have the same atomic number but different mass. e.g. Isotopes of the Hydrogen atoms are Protium (1H1), Deuterium (2H1) and Tritium(3H1). Isotopes of the Carbon atoms are 12C6, 13C6, 14C6.
Isobars are the elements that have different atomic number but have same mass number. e.g. 19K40, 18Ar40, 20Ca40, here all the elements having same mass number hence they are isobars.
Rutherford’s Alpha Scattering Experiment
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.
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 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.
- 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.
Rutherford Atomic Model
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.
Answer:
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 31X15.
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.
Answer:
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?
Answer:
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? 209X84 and 210X84
Atomic number of X is the same hence the pair shows an isotopic property. So, 209X84 and 210X84 are isotopes.
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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, (1H1).
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.