COORDINATE COVALENT BONDING
SCH 4U1
WHEN A HYDROGEN ATOM FORMS A COVALENT BOND
WITH A CHLORINE ATOM, THE PAIR OF ELECTRONS THAT THEY
SHARE BETWEEN THEM IS MADE UP OF ONE ELECTRONS FROM
EACH OF THE TWO ATOMS.
..
..
.
.
H + Cl : ----> H – Cl:
..
..
SOMETIMES ONE ATOM SUPPLIES BOTH OF THE
ELECTRONS THAT ARE SHARED IN A COVALENT BOND.
WHEN AMMONIA, NH3, IS PLACED IN AN ACIDIC
SOLUTION, IT PICKS UP A HYDROGEN ION, H+.
THIS H+ IS ATTRACTED TO THE UNPAIRED ELECTRONS OF
NITROGEN (POSITIVE ATTRACTS NEGATIVE) AND FORMS A
BOND.
H
H
+
/
:N ---H
\
H
---->
H
| +
H-N-H
|
H
SINCE BOTH THE ELECTRONS ARE SUPPLIED BY
NITROGEN, IT IS CALLED A COORDINATE COVALENT BOND.
Formal Charge = group # - # of electrons - # of bonds
Ex 1. Draw BF41- and find the formal charge of B and F.