The most non-metallic element among the given elements is

1.	Be	2.	B
3.	Mg	4.	Al

Isoelectronic pair, among the following, is : 

1. ${\mathrm{ClO}}_2^{-}, {\mathrm{ClF}}_2^{+}$

2. ${\mathrm{IF}}_2^{-}, {\mathrm{I}}_3^{-}$

3. ${\mathrm{Cl}}_2\mathrm{O}, {\mathrm{ICl}}_2^{-}$

4. ${\mathrm{ICl}}_2^{-}, {\mathrm{ClO}}_2$

The total number of 3rd period elements with more than one electron in a 3d orbital is:

The group of metals having positive value of electron gain enthalpy is :-

Percentage ionic character, if electronegativity value of X=2.1 & Y=3.0, is :-

The correctly matched option is:-

1. ${\mathrm{Fe}}^{+3}>{\mathrm{Fe}}^{+2}$ $>$ ${\mathrm{Fe}}^{+}$  : Order of atomic radius 

2. O > C > B > N   : Order of ionisation energy 

3. ${\mathrm{O}}^{-2}$ $<{\mathrm{O}}^{-}$ $<\mathrm{O}$ $<{\mathrm{O}}^{+}$ :  Increasing order of Z_eff

4. O < N < F < Ne  :  Order of electron affinity

The pair that has both members from the same period of the Periodic Table is 

Identify the INCORRECT match.

Element of the third period that is expected to exhibit positive electron gain enthalpy is: 

The atomic species that has the maximum ionization energy is :