Back to lessons
Physical SciencesGrade 1030 min

Chemical Bonding: Ionic, Covalent and Metallic

Ionic, covalent and metallic bonding — why atoms join and how the bond type explains each substance's properties.

Why atoms bond

Atoms bond to become more stable, like the noble gases with full outer shells.

Ionic bonding

A metal donates electrons to a non-metal. Sodium (2,8,1) gives its 1 electron to chlorine (2,8,7) → Na⁺ and Cl⁻ attract → NaCl (table salt). Ionic compounds form crystal lattices, have high melting points and conduct electricity when dissolved or molten.

Covalent bonding

Non-metals share electrons. In H₂O, oxygen shares one electron with each of two hydrogens. Covalent molecular substances (water, CO₂) have low melting points; covalent network substances (diamond) are extremely hard with very high melting points.

Metallic bonding

In a metal, positive kernels sit in a "sea" of delocalised electrons. This explains why metals conduct heat and electricity, and can bend without breaking.

Which bond?

  • Metal + non-metal → ionic
  • Non-metal + non-metal → covalent
  • Metal atoms → metallic

Practise

  1. What bond forms in MgO?
  2. Why does NaCl conduct when dissolved in water but not as a dry solid?
  3. Draw the Lewis diagram for H₂O.

Watch the video to see all three bond types explained.

Follow along (device voice)

Listen and follow along as each word is spoken

Why atoms bond Atoms bond to become more stable , like the noble gases with full outer shells. Ionic bonding A metal donates electrons to a non-metal. Sodium 2,8,1 gives its 1 electron to chlorine 2,8,7 → Na⁺ and Cl⁻ attract → NaCl table salt . Ionic compounds form crystal lattices, have high melting points and conduct electricity when dissolved or molten. Covalent bonding Non-metals share electrons. In H₂O, oxygen shares one electron with each of two hydrogens. Covalent molecular substances water, CO₂ have low melting points; covalent network substances diamond are extremely hard with very high melting points. Metallic bonding In a metal, positive kernels sit in a "sea" of delocalised electrons. This explains why metals conduct heat and electricity, and can bend without breaking. Which bond? - Metal + non-metal → ionic - Non-metal + non-metal → covalent - Metal atoms → metallic Practise 1. What bond forms in MgO? 2. Why does NaCl conduct when dissolved in water but not as a dry solid? 3. Draw the Lewis diagram for H₂O. Watch the video to see all three bond types explained.