Question

An alpha particle is equivalent to a:
(i) Hydrogen atom
(ii) Hydrogen ion
(iii) Helium atom
(iv) Helium ion
Rutherford’s α-particle scattering experiment showed that:
(i) electrons have negative charge
(ii) the mass and positive charge of the atom are concentrated in the nucleus
(iii) neutrons exist in the nucleus
(iv) Most of the space in an atom is empty.
(a) All of the above
(b) (i) and (iii)
(c) (i) and (iv)
(d) (ii) and (iv)

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7. For the α-particle scattering experiment Rutherford preferred gold foil
because:
(i) Gold is highly lustrous
(ii) Gold is highly malleable
(iv) Gold is less reactive
(v) None of the above

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8. Rutherford’s α-particle scattering experiment resulted in the discovery of:
(i) Electron
(ii) Proton
(iii) Nucleus in the atom
(iv) Atomic mass

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9. Which of the following is true for Thomson’s model of atom?
(i) Atom consists of neutrons
(ii) The magnitude of positive and negative charges are equal
(iii) Electrons revolve around nucleus
(iv) Protons are in the nucleus of the atom.

Answer 1

1. (iii) Helium atoms

$\alpha$ - particle scattering experiment was carried out by Ernest Rutherford. Those were "doubly charged He atoms". They were thrown to a thin gold foil of about $1000$atoms thick. The consequences were not expected.

2. (d) (ii) and (iv)

• 1/12000th particles were deflected by an angle of $180^{\degree}$ indicating the presence of positive change and mass at the middle of an atom.
• Some of alpha particles got deflected, indicating empty space inside an atom.

3. (ii) Gold is highly malleable.

E. Rutherford selected gold as it's the most malleable metal, i.e., can be hammered into thin sheets.

4. (iii) Nucleus of the atom

As we discussed before, 1/12000th particle got deflected by $180^{\degree}$ that indicated a structure present in the centre of an atom. Protons, electrons, and atomic mass were discovered by E. Goldstein, J.J. Thomson and John Dalton respectively.

5. (ii) The magnitude of positive and negative charges are equal

The atomic model of Thomson said that,

• An atom is a plum pudding like object were electrons were embedded in a positively charged sphere.
• And the magnitude of electrons were same as the positively chaged sub atomic particles.