Ionic Bonds

Ionic Bonds

• It is a chemical bond formed from the transfer of electrons from metal atoms to non-metal atoms
• Metal atoms donate valence electrons to form positive ions (cations, M^b+) and achieve the stable duplet or octet electron arrangement of the noble gases
• Non-metal atoms receive electrons to form negative ions (anions, X^a-) and achieve the stable duplet or octet electron arrangement of the noble gases
• Cations and anions are attracted to each other by strong electrostatic force of attraction

Example:

Metal	+	Non-metal	–>	Ionic compound
Sodium	+	bromine	–>	Sodium bromide
Calcium	+	chlorine	–>	Calcium chloride
Lithium	+	oxygen	–>	Lithium oxide
Aluminium	+	nitrogen	–>	Aluminium nitride

Metals
Group 1

• A lithium atom with an electron arrangement of 2.1 achieves stability after it donates one valence electron to form a lithium ion, Li⁺. The electron arrangement of the lithium ion, Li⁺, is 2 with stable duplet electron arrangement.
• A sodium atom with an electron arrangement of 2.8.1 achieves stability after it donates one valence electron to form a sodium ion, Na⁺. The electron arrangement of the sodium ion, Na⁺, is 2.8 with stable octet electron arrangement.
• A potassium atom with an electron arrangement of 2.8.8.1 achieves stability after it donates one valence electron to form a potassium ion, K⁺. The electron arrangement of the potassium ion, K⁺, is 2.8.8 with stable octet electron arrangement.

Group 2

• A magnesium atom with an electron arrangement of 2.8.2 achieves stability after it donates two valence electrons to form a magnesium ion, Mg²⁺. The electron arrangement of the magnesium ion, Mg²⁺, is 2.8 with stable octet electron arrangement.
• A calcium atom with an electron arrangement of 2.8.8.2 achieves stability after it donates two valence electrons to form a calcium ion, Ca²⁺. The electron arrangement of the calcium ion, Ca²⁺, is 2.8.8 with stable octet electron arrangement.

Group 13

• An aluminium atom with an electron arrangement of 2.8.8.3 achieves stability after it donates three valence electrons to form an alumium ion, Al³⁺. The electron arrangement of the aluminium ion, Al³⁺, is 2.8.8 with stable octet electron arrangement.

Non-metal
Group 15

• A nitrogen atom with an electron arrangement of 2.5 achieves stability after it accepts three valence electrons to form a nitride ion, N^3-. The electron arrangement of the nitride ion, N^3-, is 2.8 with stable octet electron arrangement.
• A phosphorus atom with an electron arrangement of 2.8.5 achieves stability after it accepts three valence electrons to form a phosphoride ion, P^3-. The electron arrangement of the phosphoride ion, P^3-, is 2.8.8 with stable octet electron arrangement.

Group 16

• An oxygen atom with an electron arrangement of 2.6 achieves stability after it accepts two valence electrons to form a oxide ion, O^2-. The electron arrangement of the oxide ion, O^2-, is 2.8 with stable octet electron arrangement.
• A sulphur atom with an electron arrangement of 2.8.6 achieves stability after it accepts two valence electrons to form a sulphide ion, S^2-. The electron arrangement of the sulphide ion, S^2-, is 2.8.8 with stable octet electron arrangement.

Group 17

• A fluorine atom with an electron arrangement of 2.7 achieves stability after it accepts one valence electron to form a fluoride ion, F ^-. The electron arrangement of the fluoride ion, F ^-, is 2.8 with stable octet electron arrangement.
• A chlorine atom with an electron arrangement of 2.8.7 achieves stability after it accepts one valence electron to form a chloride ion, Cl ^-. The electron arrangement of the chloride ion, Cl ^-, is 2.8.8 with stable octet electron arrangement.

Predict the Formula of an Ionic Compound

• Cation M^b+
• Anion X^a-
• Formula of an ionic compound formed, M_aX_b

Formulae for ionic compound

Metal atom, M	Non-metal atom, X	Ionic Compound
Group 1	Group 15	M3X
Group 1	Group 16	M2X
Group 1	Group 17	MX
Group 2	Group 15	M3X2
Group 2	Group 16	MX
Group 2	Group 17	MX2
Group 13	Group 15	MX
Group 13	Group 16	M2X3
Group 13	Group 17	MX3

Some common ionic compound

• Sodium chloride (NaCl)
• Magnesium oxide (MgO)
• Calcium sulphide (CaS)
• Potassium oxide (K₂O)
• Magnesium fluoride (MgF₂)

Structure of ionic compounds

• The oppositely-charged ions, M^b+ and X^a- are attracted to each other by a strong electrostatic force.
• It form a rigid 3-dimensional lattice structure
• Formed crystal.
• Giant ionic lattice.

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