Page 3 - Microsoft Word - Module-4

(c)Nitrates:

Nitrates of alkaline earth metals are obtained by reaction

of carbonates with dil. HNO3.They decompose on

heating.

2M(NO )  2MO + 4NO + O ;M= Alkaline earth metal
2
2
3 2
ANOMALOUS BEHAVIOUR OF Be

 Be has smallest size and highest ionization energy.

 It forms predominately covalent compounds which

are readily hydrolysed.

 It forms amphoteric oxides and hydroxides while

others form basic oxides and hydroxides.

 Be can show coordination number of four, others

show higher coordination number.

 It does not react with H O even on red hot.
2
DIAGONAL RELATIONSHIP BETWEEN Be AND Al

 They have similar electronegativity.

 Both form amphoteric oxides and hydroxides.

 Both become passive due to formation of oxide

layer.

 BeCl and AlCl have bridged structure in vapour
3
2
phase.

2_
_
 Both form hydroxide ions [Be(OH) ] and [ Al(OH) ]
4
4
in aqueous alkali solution.