Page 2 - Microsoft Word - P-BLOCK ELEMENTS LN-1

TRENDS IN CHEMICAL PROPERTIES

OXIDATION STATE: Boron does not form +3 ions due to very high
energy is needed to remove 3 electrons. Down the group the stability

of +1 oxidation state increases but +3 oxidation state decreases due
to inert pair effect. In ‘Tl’ +3 oxidation state is highly oxidizing in

nature.

• In trivalent state , most of compounds being covalent are

hydrolysed by water and exit as [M(OH)4]-,

ℎ , ℎ ℎ .[ ( 2 )6] is

hybridized, octahedral shaped.
REACTIVITY TOWARDS AIR

Δ Δ
2E(s) + 3O2 (g) → 2E2O3(s) , 2E(s) + N2 (g) → 2EN(s)

(E= Gr.13element).Aluminium and gallium oxides are amphoteric
and those of indium and thallium are basic in their properties.

REACTIVITY TOWARDS ACIDS AND ALKALIES
• Boron does not react with dil.acids as well as alkalies even at

moderate temperature.
• 2Al(s) + 6HCl (aq) → 2Al3+ (aq) + 6Cl– (aq) + 3H2 (g)

• 2Al (s) + 2NaOH(aq) + 6H2O(l) → [ ( ) ]

(aq)+3H2(g)

Sodium tetrahydroxo

aluminate(III)

REACTIVITY TOWARDS HALOGENS: These elements react with halogens

to form trihalides (except Tl I3). 2E(s) + 3 X2 (g) → 2EX3 (s) (X = F, Cl, Br,
I) ANOMALOUS PROPERTIES OF BORON :Reason: i. exceptionally
small atomic and ionic size ii. High I.E iii.absence of d- orbitals in

valence shell.