Electron affinity is the :

1. Power of an atom to attract an electron to itself.
2. Energy released when an electron is added to an isolated atom in the gaseous state.
3. Energy absorbed when an electron is added to an isolated atom in the gaseous state.
4. Energy required to remove an electron from an isolated gaseous atom.

Which of these statements gives the correct picture regarding halogens and alkali metals with respect to an increase in the atomic number ?

1. Reactivity decreases in alkali metals but increases in halogens.
2. Reactivity increases in both.
3. Reactivity decreases in both.
4. Reactivity increases in alkali metals but decreases in halogens.

An element ₁₃X combines with ₁₇Y to form a compound. which of the following is true ?

P → X is a metal, Y is a metal.
Q → X is a metal, Y is a non-metal.
R → X losses electron(s), y gains electron(s).

1. Only P
2. Only Q
3. Both P and Q
4. Both Q and R

Assertion (A): Second period consists of 8 elements.

Reason (R): Number of elements in each period is four times the number of atomic orbitals available in energy level that is being filled.

1. Both A and R are true and R is the correct explanation of A.
2. Both A and R are true but R is not the correct explanation of A.
3. A is true but R is false.
4. A is false but R is true.