For the second-period elements, the correct increasing order of first ionisation enthalpy is:

1.	Li < Be < B < C < O < N < F < Ne
2.	Li < Be < B < C < N < O < F < Ne
3.	Li < B < Be < C < O < N < F < Ne
4.	Li < B < Be < C < N < O < F < Ne

A configuration with the lowest ionization enthalpy among the following is:
1. \(1 s^2 2 s^2 2 p^5\)$\mathrm{}$
2. \(1 s^2 2 s^2 2 p^3\)
3. \(1 s^2 2 s^2 2 p^6 3 s^1\)
4. \(1 s^2 2 s^2 2 p^6\)

The correct order of the decreasing ionic radii among the following isoelectronic species is:

1. $C{a}^{2+}>K^{+}>S^{2-}>C{l}^{-}$

2. $C{l}^{-}>S^{2-}>C{a}^{2+}>K^{+}$

3. $S^{2-}>C{l}^{-}>K^{+}>C{a}^{2+}$

4. $K^{+}>C{a}^{2+}>C{l}^{-}>S^{2-}$

The correct order of ionic radii is:

1. $H^{-}>H^{+}>H$ $$
2. $N{a}^{+}>F^{-}>O^{2-}$
3. $F^{-}>O^{2-}>N{a}^{+}$
4. $N^{3-}>M{g}^{2+}>A{l}^{3+}$

Which of the following third-period elements has a positive electron gain enthalpy?

The most non-metallic element among the given elements is

In alkaline earth metals, the properties, among the following, that will increase from Be to Ba are:

(i) Atomic radius
(ii) Ionisation energy
(iii) Nuclear charge

Consider the following periodic properties:

(i) Atomic radius
(ii) Electronegativity
(iii) Ionisation energy
(iv) Metallic character
Which of these properties decrease from left to right across a period and increase from top to bottom down a group?

Consider the following electronic configuration of an element (P) :

$\left[\mathrm{Xe}\right]4{\mathrm{f}}^{14}5{\mathrm{d}}^{1}6{\mathrm{s}}^2$

The correct statement about element 'P' is :

1. It belongs to the 6th period and the 1st group.

2. It belongs to the 6th period and the 2nd group.

3. It belongs to the 6th period and the 3rd group.

4. None of the above.