Page 51 - Chemistry ICSE Class X

Chemical Bonding 39
Due to the mutual sharing of two pairs of electrons, each oxygen atom
CESWKTGU UVCDNG GNGEVTQPKE EQPſIWTCVKQP QH PGQP VJG PGCTGUV PQDNG ICU
What is a triple covalent bond

The covalent bond formed by mutual sharing of three pairs of electrons
between the combining atoms is termed as triple covalent bond or simply ƚŚLJŶĞ ; , Ϳ ŝƐ Ă ŵŽůĞĐƵůĞ ƚŚĂƚ
Ϯ Ϯ
ĐŽŶƚĂŝŶƐ ƚǁŽ ʹ , ƐŝŶŐůĞ ďŽŶĚƐ ĂŶĚ
as triple bond. A triple bond is denoted by a set of three dashes ({). For ŽŶĞ ĐĂƌďŽŶͲĐĂƌďŽŶ ƚƌŝƉůĞ ďŽŶĚ͕
example, two nitrogen atoms share three pairs of electrons to form a ; { Ϳ͘
molecule of nitrogen (N ). Thus, in nitrogen molecule, the two nitrogen , ʹ { ʹ ,
2
atoms are bonded to each other by a triple bond. Due to this mutual sharing, ĞƚŚLJŶĞ
DQVJ VJG PKVTQIGP CVQOU CESWKTG C UVCDNG EQPſIWTCVKQP QH PGQP

What conditions favour the formation of covalent bonds
6JG HQNNQYKPI EQPFKVKQPU HCXQWT VJG HQTOCVKQP QH EQXCNGPV DQPF
ƒ Both the atoms should have JKIJ KQPKUCVKQP GPGTI[, so that electron
transfer is not possible.
ƒ Both the atoms should have JKIJ GNGEVTQP CHſPKV[.
ƒ Both the atoms should have JKIJ GNGEVTQPGICVKXKV[.
ƒ The difference between the electronegativities of the combining atoms
should either be zero or small.
What are the bonding and lone pair of electrons
The shared pair of electrons located in between the two combining atoms is
called the DQPFKPI RCKT QH GNGEVTQPU.
A pair of electrons located on any atom, which does not take part in the
bonding process is called lone-pair of electrons. The lone-pair of electrons
is also called nonbonding pair of electrons.
The bonding and the lone-pair of electrons in ammonia (NH ) molecule
3
are shown alongside.
What are the characteristics of a covalent bond
%QXCNGPV DQPFU JCXG VJG HQNNQYKPI EJCTCEVGTKUVKEU
ƒ Covalent bonds are formed by OWVWCN UJCTKPI of electrons.
ƒ Covalent bonds are directional. This is because the shared pair of
GNGEVTQPU TGOCKP NQECNKUGF KP FGſPKVG URCEG DGVYGGP VJG VYQ CVQOU
ƒ Covalent bonds are strong, and are not broken by heating.

Structures of Some Covalent Compounds and
Molecules

%QXCNGPV OQNGEWNGU EQORQWPFU CTG HQTOGF D[ VJG OWVWCN UJCTKPI QH
electrons between the combining atoms. Structures of some typical covalent
OQNGEWNGU EQORQWPFU CTG FGUETKDGF DGNQY

Hydrogen molecule (H )
2
K
6JG GNGEVTQPKE EQPſIWTCVKQP QH J[FTQIGP KU . Thus, hydrogen atom has
1
only one electron in its outermost shell, and requires one more to acquire
)
VJG PGCTGUV PQDNG ICU EQPſIWTCVKQP ( *G K . To do so, two hydrogen atoms
2