The value of electron gain enthalpy of Na⁺, if IE₁ of Na = 5.1 eV, is:

1. +10.2 eV 

2. –5.1 eV

3. –10.2 eV 

4. +2.55 eV

Among the elements Ca, Mg, P and Cl, the correct order of increasing atomic radii is:
1. Cl < P < Mg < Ca
2. P < Cl < Ca < Mg
3. Ca < Mg < P < Cl
4. Mg < Ca < Cl < P

Which one of the following orders is not in accordance with the property stated against?

1. $F_2>C{l}_2>B{r}_2>I_2$ $:$ $Oxidi\sin g$ $power$

2. $Hl>HBr>HCl>HF$ $:$ $Acidic$ $property$ $in$ $water$

3. $F_2>C{l}_2>B{r}_2>I_2$ $:$ $Electronegativity$

4. $F_2>C{l}_2>B{r}_2>I_2$ $:$ $Bond$ $dissociation$ $energy$

Identify the correct order of the size of the following:

1. $C{a}^{2+}<K^{+}<Ar<S^{2-}<C{l}^{-}$

2. $C{a}^{2+}<K^{+}<Ar<C{l}^{-}<S^{2-}$

3. $Ar<C{a}^{2+}<K^{+}<C{l}^{-}<S^{2-}$

4. $C{a}^{2+}<A{r}^{+}<K^{+}<C{l}^{-}<S^{2-}$

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. \(1 s^2 2 s^2 2 p^6\)

Among the following, the most characteristic oxidation states for lead and tin are, respectively:

1. +4, +2

2. +2, +4

3. +4, +4

4. +2, +2

Amongst the elements with the following electronic configurations, which one of them may have the highest ionisation energy?

1. $\left[Ne\right]$ $3s^2$ $3p^3$

2. $\left[Ne\right]$ $3s^2$ $3p^2$

3. $\left[Ar\right]$ $3d^{10}$ $4s^2$ $4p^3$

4. $\left[Ne\right]$ $3s^2$ $3p^1$