Rutherford's alpha–particle scattering experiment was responsible for the discovery of

1. Atomic nucleus
2. Electron
3. Proton
4. Neutron

Isotopes of an element have

1. The same physical properties
2. Different chemical properties
3. Different number of neutrons
4. Different atomic numbers

Number of valence electrons in Cl^- ion are

1. 16
2. 8
3. 17
4. 18

Which one of the following is a correct electronic configuration of Sodium?

1. 2, 8
2. 8, 2, 1
3. 2, 1, 8
4. 2, 8, 1