Page 1 - Microsoft Word - P-BLOCK ELEMENTS LN-4

TRENDS IN CHEMICAL PROPERTIES

• i. OXIDATION STATE:The common oxidation states exhibited by
these elements are +4 and +2. In heavier members the tendency

to show +2 oxidation state increases in the sequence Ge<Sn<Pb.

• C and Si mostly show +4 oxidation state.Ge forms stable
compounds in +4 state and only few compounds in +2 state. Sn

forms compounds in both oxidation states (Sn in +2 state is a

reducing agent). Pb compounds in +2 state are stable and in +4
state are strong oxidising agents.

ii.Reactivity towards oxygen : Oxides in higher oxidation states of
elements are more acidic than those in lower oxidation states.

• The dioxides— CO2, SiO2 and GeO2 are acidic, whereas SnO2 and

PbO2 are amphoteric in nature.Among monoxides, CO is neutral,
GeO is distinctly acidic whereas SnO and PbO are amphoteric.

• iii.Reactivity towards water :C, Si and Ge are not affected by water.

Pb is unaffected by water, due to protective oxide film formation.

Δ
• Sn + 2H2O → SnO2 + 2H2

Reactivity towards halogen: Form halides MX2 and MX4 (where X = F,
Cl, Br, I). Except carbon, all other members react directly with halogens.

PbI4 does not exist due to inert pair effect. Except CCl4, other

tetrachlorides are easily hydrolysed by water