8.2 Ionic Bonding
Ionic Bonds
• Ionic bonds are made between metal
and non-metal atoms
• Electrons are transferred from the metal
atom to the non-metal atom
• Metal atoms lose electrons form positive
ions called cations.
• Non metal atoms gain electrons form
negative ions called anions.
Metals
• Metals atoms lose electrons to form positive
ions (an atom that loses or gains electrons)
called cations.
E.g., Beryllium (Be) Group 2
Neutral atom
4+ P’s
4- E’s
0
Positive ion
4+ P’s
2- E’s
2+
Valence Electrons
The electrons in the outer shell of an atom, which determines its
power to combine with other elements
Non-metals
• Non-metal atoms gain electrons to form
negative ions called anions.
E.g., Carbon (Ca) Group 14
Neutral atom
6+ P’s
6- E’s
0
Negative ion
6+ P’s
10- E’s
4-
An example of ionic
bonding…..
• Let us consider the bonding in the
substance sodium chloride.
• Na+ + ClNa+Cl• In this reaction the sodium (Na) atom
loses 1 electron while the chlorine atom
accepts the electron in the transfer
process.
NaCl
• Thus we can say that sodium chloride is an
ionic compound
NaCl
Na+
Sodium ion
This charged
atom contains:
11+ Protons
+ 10- Electrons
-1
ClChloride ion
This charged atom
contains:
17+ Protons
+ 18- Electrons
+1
Sodium Chloride
• Thus NaCl
• Once these two ions (An atom that has
become charged be gaining or losing
one or more electrons) have been
formed, they will attract each other
because of their opposite charges
CaO
• Ca2+ + O2Ca2+O2• In this reaction the calcium (Ca) atom
loses 2 electrons while the oxygen (O)
atom accepts the two electrons in the
transfer process.
Thus we can say that calcium oxide is an
ionic compound
Calcium Oxide
Ca2+ Calcium ion
20+ Protons
18- Electrons
2+
O2- Oxide ion
8+ Protons
10- Electrons
2-
Once these two ions have been formed, they will
attract each other because of their opposite charges.
There is an electrostatic attractive force present (like
charges repel and unlike charges attract) that creates
the chemical bond in the NaCl and CaO,called an
ionic bond.
Let’s try one…..
Magnesium and Fluorine
Metal
12+ Protons
10- Electrons
2+
Mg2+ + F1-
Non-metal
9+ Protons
10- Electrons
1Mg2+F1-
Chemical name: Magnesium fluoride
Chemical Formula: MgF2
• Group 1 elements form cations with one positive
charge.
• Group 2 elements form cations with two positive
charges.
• Group 3 elements form cations with three positive
charges.
• Group 17 elements form anions with one negative
charge.
• Group 16 elements form anions with two negative
charges.
• group 15 elements form anions with three negative
charges.
Group number on the periodic table indicates the
number of electrons the atom will lose or gain.
Figuring out Ionic Charge
• For metals, it‘s the same as the
group number (the column number).
• For non metals, the charge is equal to
whatever number needs to be added
to the group number to get 8. Group 8,
(the noble gases), don‘t form ions as
they do not need to gain any electrons
to have a full outer shell
More to try……..
Potassium and Sulfur
Aluminium and Chlorine
Aluminum and Oxygen
Calcium and Fluorine
Bonding in Ionic Compounds
• According to the ionic electrostatic model, solids such as
NaCl consist of positive and negative ions arranged in a crystal
lattice.
• Each ion is attracted to neighbouring ions of opposite charge,
and is repelled by ions of like charge; this combination of
attractions and repulsions, acting in all directions, causes the ion
to be tightly fixed in its own location in the crystal lattice.
Sodium metal reacts with chlorine gas in a violently exothermic
reaction to produce NaCl (composed of Na+ and Cl- ions):
2Na(s) + Cl2(g) -> 2NaCl(s)