Question

describe the important physical differences and a chemical difference between each of the hydrogen compounds of the p-block elements in period 2 and their counterparts in period 3

Answer 1

Solution:

There are eight elements in the second group out of those six elements (boron, carbon, nitrogen,oxygen, fluorine and neon) belong to p-block. The third period contains eight elements: sodium, magnesium, aluminium, silicon, phosphorus, sulfur, chlorine, and argon are lies in p block of the periodic table.The second group p-block elements form BH₃,CH₄,NH₃,H₂O,HF componds,while third group compounds form AlH3, SiH4, PH3,H2S, HCl.

. The second groupp block elements form covalent hydrides. This occurs when hydrogen covalently bonds to a more electropositive element by sharing electron pairs. These hydrides can be volatile or non-volatile. One such example of a covalent hydride is when hydrogen bonds with chlorine and forms hydrochloric acid (HCl).The hydrides of nonmetals on the periodic table become more electronegative as we move from left to right (B to F).

Only some hydrides are capable to form hydrogen bonding. Hydrogen bonds have energies of the order of 15-40 kJ/mol, which are fairly strong but weaker than covalent bond. Specifically fluorine, oxygen, and nitrogen are more vulnerable to hydrogen bonding.This type of bonding is generaly absent in the third period p block elements.

The presence of vacant d orbitals in the third period of elements responsible for maximum covalency. Due to more electronegative character of F, it form more stable covalent HF molecule. The noble metals (Ne and Ar) are unreactive, hence not capable to form hydrogen compounds.