Page 53 - Chemistry ICSE Class X

Chemical Bonding 41

Ammonia molecule (NH )
3
6JG GNGEVTQPKE EQPſIWTCVKQPU QH PKVTQIGP CPF J[FTQIGP CTG
0KVTQIGP K L *[FTQIGP K
,
2 5
1
Thus, the nitrogen atom needs three electrons to complete its octet,
while each hydrogen atom needs only one electron to complete its duplet.
To do so, three hydrogen atoms tend to share one electron pair each
with the nitrogen atom.

There are three single covalent bonds in a molecule of ammonia. The
×
unshared pair of electrons on the nitrogen atom of ×NH does not take part
3
in bond formation. Therefore, it is called a lone-pair of electrons.
Methane molecule (CH )
4
Methane molecule contains one atom of carbon and four atoms of hydrogen,
i.e., the molecular formula of methane is CH 6JG GNGEVTQPKE EQPſIWTCVKQP
4
of carbon is 2, 4 and that of hydrogen is 1.
Carbon atom in CH thus shares 4 pairs of electrons, one pair with each
4
hydrogen atom, i.e.,

In methane, carbon atom is linked to four hydrogen atoms by four
C – H single bonds.

Carbon tetrachloride molecule (CCl )
4
( )
KL
6JG GNGEVTQPKE EQPſIWTCVKQP QH ECTDQP KU 24 and that of chlorine is
,
K L M
2 8 7 . The carbon atom needs four electrons to complete its octet, and
each chlorine atom requires only one electron to complete its octet. Thus,
each chlorine atom shares one electron pair with carbon atom, i.e.,