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.

Assertion (A): In a Dobereiner's triad, the three elements present have the same difference of atomic masses.

Reason (R): Elements in a triad have similar properties.

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.

Assertion (A): Hydrogen is placed in group I.

Reason (R): Hydrogen can gain an electron to achieve noble gas configuration.

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.

Assertion (A): Atomic size increases along a period.

Reason (R): Effective nuclear charge increases with atomic number.

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.