The correct order of the atomic radii of C, Cs, Al, and S is :

The electronegativity of aluminium is similar to :

When the first electron gain enthalpy $$\left( {{\Delta _{eg}}H} \right)$$ of oxygen is $$-$$ 141 kJ/mol, its second electron gain enthalpy is :

In general, the properties that decrease and increase down a group in the periodic table, respectively, are :