A very basic look at the dative covalent bond. It is normally met at CAPE, but recently has been introduced to students in form three. It is that form three occurrence which really prompted this piece of work

1. INTRODUCTION TO
THE
DATIVE COVALENT
DATIVE COVALENT
BOND
FOR
CAPE UNIT 1
CAPE UNIT 1
CHEMISTRY STUDENTS
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2. This is a special type of covalent
bond in which both the shared
electrons are contributed b one
l
b d by
atom only
only.
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3. It can be defined as
“a covalent bond in which both
a
electrons of the shared pair
are contributed b one
b d by
of the two atoms”
f
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4. Such bond
S h a b d iis also referred t
l
f
d to
as a
co-ordinate bond.
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5. A co-ordinate or dative covalent bond is
established between two atoms where:
(a) One of the two atoms has a full outer
shell and a non bonding pair of
non-bonding
electrons.
(b) Th other atom is one pair short of a
The th
t
i
i h t f
f
full outer shell of electrons.
f
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6. Examples of such atoms are
A and B, below:
B
x x
B
x x
. .
.
. .
.
. .
A
. .
..
x x
x x
When A and B combine A contributes both
combine,
electrons to the covalent bond;
B contributes none.
none
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7. The compound AB can be represented as
. .
B
x x
A
x x
. .
. .
. .
x x
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8. AB can also be shown as
x x
A →B
. .
x x
. .
. .
x x
The covalent bond is represented by an arrow
(→) pointing towards the acceptor atom.
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9. The t
Th atom which contributes th electron
hi h
t ib t the l t
pair is called the donor, while the atom
which accepts it is called the acceptor.
h h
ll d h
The dative covalent bond once formed is
bond,
indistinguishable from a (regular)
covalent bond.
bond
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10. The compound formed via dative
bonding can be called:
(a) A coordinate compound.
compound
(b) An addition compound.
p
(c) An adduct.
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11. Examples Of
Coordinate
Bond
Formation
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12. Combination of ammonia and boron trifluoride
The it
Th nitrogen atom iin ammonia h a f ll outer shell, iinclusive of
t
i has full
t
h ll
l i
f
a lone pair which it can donate.
The b
h boron atom in b
boron trifluoride is short of two electrons
fl
d
h
f
l
which it accepts to attain a full outer shell.
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14. Formation of ammonium ion
The hydrogen iion, H+, h no electrons and accepts
Th h d
has
l t
d
t
a lone pair donated by nitrogen.
After accepting the lone pair, hydrogen
has a full outer shell.
shell
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16. Characteristics Of Coordinate
Compounds
(a)
Their melting and b l
h
l
d boiling points are h h than purely
higher h
l
covalent compounds but lower than ionic compounds.
(b)
They are sparingly soluble in polar solvents like water but
readily soluble in non polar (organic) solvents
non-polar
solvents.
(c)
Like covalent compounds they are also poor conductors
compounds,
of electricity. Their solutions or fused states also do not
conduct.
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17. END
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