10. Ionic Bonding | Chemistry

What is an ionic bond?

An ionic bond forms between a metal and a non-metal.

The metal atom loses its valence electrons and becomes a positive ion.
The non-metal atom gains those electrons and becomes a negative ion.
The opposite charges attract strongly. That attraction is the ionic bond.

$Na (2, 8, 1) \to N a^{+} (2, 8) + e^{-} Cl (2, 8, 7) + e^{-} \to C l^{-} (2, 8, 8)$

Only the outer electrons are drawn. Sodium's one outer electron moves to the gap in chlorine's outer shell.

Charges of common ions

The charge of an ion comes from its group.

Group	1	2	13	15	16	17
Valence electrons	1	2	3	5	6	7
Ion charge	$+ 1$	$+ 2$	$+ 3$	$- 3$	$- 2$	$- 1$
Example	$N a^{+}$	$M g^{2 +}$	$A l^{3 +}$	$N^{3 -}$	$O^{2 -}$	$C l^{-}$

Writing ionic formulas

An ionic compound has no overall charge. The positive and negative charges must cancel.

Naming ionic compounds

Name the metal first, unchanged.
Name the non-metal second, with the ending changed to -ide.

Non-metal	Ion name
Chlorine	chloride
Oxygen	oxide
Sulfur	sulfide
Nitrogen	nitride
Fluorine	fluoride

$MgO$ is magnesium oxide. $L i_{3} N$ is lithium nitride.

Polyatomic ions

Some ions are groups of atoms bonded together that carry a charge as a whole.

Ion	Formula	Ion	Formula
Hydroxide	$O H^{-}$	Carbonate	$C O_{3}^{2 -}$
Nitrate	$N O_{3}^{-}$	Sulfate	$S O_{4}^{2 -}$
Ammonium	$N H_{4}^{+}$	Phosphate	$P O_{4}^{3 -}$

Treat them as one unit. If you need more than one, use brackets: calcium hydroxide is $Ca (OH)_{2}$ , ammonium sulfate is $(N H_{4})_{2} S O_{4}$ .

Ionic lattices and their properties

Ionic compounds do not form separate molecules. Millions of ions pack into a regular 3D pattern called an ionic lattice, each ion surrounded by ions of the opposite charge. That is why salt forms neat cube-shaped crystals.

Property	Reason
High melting and boiling points (salt melts at 801 °C)	Strong attraction between ions in every direction takes a lot of energy to break
Hard but brittle	A hit shifts a layer, like charges line up and repel, and the crystal shatters
Do not conduct as solids	Ions are locked in place
Conduct when melted or dissolved	Ions are free to move and carry charge
Many dissolve in water	Water molecules pull the ions apart

Ionic bonding

Who

Metal + non-metal

How

Metal loses e⁻: positive ion
Non-metal gains e⁻: negative ion
Opposites attract

Formulas

Charges cancel to zero
Swap and drop
Brackets for polyatomic ions

Names

Metal first
Non-metal ends in -ide

Lattice properties

High melting point
Brittle
Conducts when molten or dissolved

Quick summary

Ionic bonds form between a metal and a non-metal.
Metals lose electrons (positive ions). Non-metals gain electrons (negative ions). Opposite charges attract.
Formulas: charges must add to zero. Use swap and drop, then simplify.
Names: metal first, non-metal ending in -ide. Polyatomic ions keep their own names.
Ionic lattices have high melting points, are brittle, and conduct only when molten or dissolved.

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