🎓 Prepared by students from Boğaziçi University

What is Ionic Bonding?

Ionic bonding is the electrostatic attraction between a positively charged cation and a negatively charged anion. It's the primary bonding in salts and ionic compounds, and it occurs when one atom transfers electrons to another.

Short answer

Ionic bonds form when a metal atom loses electrons to a non-metal, creating a cation and an anion that attract each other electrostatically. The bond is very strong in solid form but breaks easily in water.

Ionic Bond Formation: Na + Cl → NaCl

1
1. Sodium Atom
11 protons, 11 electrons (neutral)
↓
2
2. Loses 1 electron
Becomes Na⁺ cation (11 p, 10 e)
↓
3
3. Chlorine Atom
17 protons, 17 electrons (neutral)
↓
4
4. Gains 1 electron
Becomes Cl⁻ anion (17 p, 18 e)
↓
5
5. Electrostatic Attraction
Na⁺ and Cl⁻ bond: ionic solid NaCl

Step-by-step worked examples

Write the ionic bond formula when magnesium (12p, loses 2e) bonds with oxygen (8p, gains 2e).

Mg loses 2 electrons → Mg²⁺ (12p, 10e)
O gains 2 electrons → O²⁻ (8p, 10e)
Electrostatic attraction between Mg²⁺ and O²⁻
Ionic compound: MgO

Aluminum (Al, 13 protons) loses 3 electrons to fluorine (F, 9 protons). What compound forms?

Al loses 3 electrons → Al³⁺ (13p, 10e)
F gains 1 electron → F⁻ (9p, 10e)
For charge balance: 1 Al³⁺ bonds with 3 F⁻
Compound: AlF₃

In CaCl₂, identify the cation and anion, and their charges.

Ca = Calcium (metal) → loses 2 electrons → Ca²⁺
Cl = Chlorine (non-metal) → gains 1 electron → Cl⁻
1 Ca²⁺ bonds with 2 Cl⁻ (charge balance: +2 and 2×−1)

Flashcards

Quick quiz

Q1.Ionic bonds form when one atom ___ electrons to another.

Correct answer: B. Ionic bonding involves electron transfer, creating a cation and an anion.

Q2.Which compound is ionic?

Correct answer: C. NaCl (sodium chloride) is ionic. Others are covalent or molecular.

Q3.Why do ionic compounds have high melting points?

Correct answer: C. Ionic compounds have strong electrostatic attractions in their 3D lattice.

Q4.In the compound CaO, what is the charge on Ca?

Correct answer: B. Calcium (metal) loses 2 electrons → Ca²⁺. Charge = +2.

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Common mistakes

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Ionic bonds are covalent bonds. — Correct: Ionic bonds form by electron transfer; covalent bonds form by electron sharing.

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Ionic compounds are always soluble in water. — Correct: Many ionic compounds are soluble (like NaCl), but some are insoluble (like AgCl).

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Ionic bonding only involves one electron transfer. — Correct: An ion can have charge +2, +3, −2, −3, etc., depending on electrons transferred.

✗

Ionic bonds exist in the gas phase. — Correct: Ionic bonds are strong in solids (lattice structure). In gas, ionic compounds break apart into atoms.

FAQ

What determines which element loses electrons?

The element with lower ionization energy (usually a metal) loses electrons more easily to the element with higher electron affinity (usually a non-metal).

Can non-metals form ionic bonds with each other?

Rarely. Ionic bonds form primarily between metals and non-metals because of the large difference in electronegativity.

Why do ionic compounds conduct electricity when melted or dissolved?

Melting or dissolving breaks the solid lattice, freeing the ions to move and carry electric current.

What is an ionic lattice?

A 3D repeating pattern of cations and anions in a solid ionic compound. Each ion is surrounded by oppositely charged ions.