The formula of the oxide of an element $M$ having $IE_1 = 100 \ kJ/mol$,$IE_2 = 250 \ kJ/mol$ and $IE_3 = 1500 \ kJ/mol$ should be:

The correct statement regarding $ClO_n^-$ molecular ion is

What is valency? Explain.

Explain the periodicity of valence or oxidation states and explain the oxidation states of oxygen in $Na_2O$ and $OF_2$.

Predict the formulas of the stable binary compounds that would be formed by the combination of the following pairs of elements.
$(a)$ Lithium and oxygen
$(b)$ Magnesium and nitrogen
$(c)$ Aluminium and iodine
$(d)$ Silicon and oxygen
$(e)$ Phosphorus and fluorine
$(f)$ Element $71$ and fluorine

Number of elements from the following that $CANNOT$ form compounds with valencies which match with their respective group valencies is
$B, C, N, S, O, F, P, Al, Si$