The Correct Order According To Size Is

The first ionisation energy of oxygen is less than that of nitrogen. Which of the following is the correct reason for this observation?

The charge/size ratio of a cation determines its polarizing power. Which one of the following sequences represents the increasing order of the polarizing power of the cationic species, K⁺, Ca²⁺, Mg²⁺, Be²⁺? 

Which one of the following arrangements represents the correct order of electron gain enthalpy (with negative sign) of the given atomic species?

Which is likely to show inert pair effect?

The correct order of the size of iodine species is

In which one of the following pairs the radius of the second species is greater than that of the first?

The increasing order of the first ionisation enthalpies of elements B, P, S and F (lowest first) is

The element having highest electron affinity is

Diagonal relationship is for

The successive ionisation energy values for an element ‘X’ are given below: 

1^st ionisation energy = 410 kJ mol^–1

2^nd ionisation energy = 820 kJ mol^–1

3^rd ionisation energy = 1100 kJ mol^–1

4^th ionisation energy = 1500 kJ mol^–1

5^th ionisation energy = 3200 kJ mol^–1

Find out the number of valence electrons for the atom ‘X’.