Trends in the Periodic Table and Bonding
Bonding Continuum
Ionic Bonds
Ionic bonds are formed between atoms with a large
difference in electronegativities. They are often
(though not always) between metals and non-metals.
For example, in potassium bromide, the difference in
electronegativities is so large that potassium will lose
an electron and form a positive ion.
Bromine gains this electron and forms a negative ion.
The ionic bond is the electrostatic force of attraction
between a positive and negative ion.
Reacting Elements:
Ke-
Br
Electron Arrangement:
2,8,8,1
2,8,7
During Reaction:
loses 1e-
gains 1e-
transfer of
an electron
+
Ions Formed:
K
New Electron
Arrangement:
2,8,8
Br
-
2,8,8
The electrostatic force of attraction between the
oppositely charged ions is called the ionic bond
K
+
Br
-
Ionic compounds form a LATTICE STRUCTURE.
Millions of oppositely charged ions are held
together in a very stable arrangement.
Bonding Continuum
We can place each of the types of intermolecular
bond in one continuous series based on how much
ionic character the bond displays.
This is governed by the difference in
electronegativities between the two atoms.
Increasing ionic character
Pure Covalent Bonding
A pure covalent bond has no ionic character at all.
The electronegativities of both atoms are identical and
the bonding electrons are evenly shared between
both atoms.
H
e
e
H
2.2
Increasing
ionic character2.2
Electronegativities
H
e
e
H
Increasing ionic character
Polar Covalent Bonding
There
A
polariscovalent
a small difference
bond has some
between
ionic
the
character.
electronegativities of both atoms and the bonding
electrons are pulled more closely to the more
electronegative atom.
δ-
δ+
P
e
Cl
e
2.2
H
δ+
e
e
3.0
H
e
δ-
Cl
P
e
Electronegativities
Increasing ionic character
Ionic Bond
An
ionic
existsof
when
the difference
in
There
is bond
no sharing
the electrons
and oppositely
electronegativities
is so great that the movement of
charged ions are formed.
the bonding electrons between the two atoms is
complete.
Li
+
F
e
e
1.0
H
e
e
H
4.0
δδ+
e
Electronegativities
Cl
P
e
Increasing ionic character
Li
+
F
-
Bonding Continuum
Pure
Covalent
Bond
Polar
Covalent
Bond
Ionic
Bond
To judge the type of bonding in any particular
compound it is more important to look at the
properties it exhibits rather than simply the names of
δδ+
e
e
the
elements
involved.
Cl
H
P
H
Li
F
+
e
e
Increasing ionic character
-