The correct statement about radius is :

1.	Radius increases during cation and anion formation.
2.	Radius increases during anion formation and decreases during cation formation.
3.	Radius decreases in cation as well as anion.
4.	Radius decreases during anion formation and increases during cation formation.

The values of first ionization enthalpies for two isotopes would be -

The reactivity of alkali metals increases, whereas halogen decreases down the group, because -

The general outer electronic configuration of s, p, d , and f-block elements respectively would be :

The position of elements with an outer electronic configuration as $(n-2) f^7(n-1)d^{1}n{s}^2, n = \mathrm{6\; :}$

1. 6^th period and 10^th group.

2.  7^th period and 3^rd group.

3.  6^th period and 3^rd group.

4. 7^th period and 9^th group.

1st (∆H₁) and 2nd  (∆H₂) Ionization Enthalpies (in kJ mol^–1) and the (∆_egH) Electron Gain Enthalpy (in kJ mol^–1) of a few elements are given below:

The most reactive metal is-
1. VI
2. III
3. I
4. II

The formula of the stable binary compounds that would be formed by 
an element having atomic number 71 and fluorine:

The factor that does not affect the valence electron is: 

The size of isoelectronic species: F^–, Ne and Na⁺, is affected by :

The incorrect statement about ionization enthalpy is -