The p -Block Elements

Kindly consider the following Image 

At room temperature water is liquid and has boiling point 373K due to hydrogen bonding. Where as H? S is gas and it has no hydrogen bonding. Hence boiling point of H? S is less than 300K [Boiling point of H? S is -60 °C ].

(1) Pb (NO? )? → PbO + 2NO?
(2) NH? NO? → N? + 2H? O
(3) (NH? )? Cr? O? → N? + Cr? O? + H? O
(4) NaN? → 3N? + 2Na

Gypsum $\stackrel{393\mathrm{K}}{?}{\mathrm{C}\mathrm{a}\mathrm{S}\mathrm{O}}_4\frac{1}{2}{\mathrm{H}}_2\mathrm{O}$

When positive charge increases, ionic radii decreases in isoelectronic ions
Al?³ < Mg? < Na? < K?

[SiCl?]?² is not known because six larger chloride ions can't be accomodated around Si? due to its small size.