2.1.1Structure, Bonding and the Properties of Matter
Chemical Bonding
5 min read 4 parts Lesson 2 of 14 Unit quiz
Section 1 of 4Why Atoms Bond
Atoms bond in order to become chemically stable, which means having a full outer shell like a noble gas.
Compound
- A substance in which atoms of two or more elements are chemically combined.
Stability
- Atoms combine to achieve a full outer shell of electrons, which is the same arrangement as a noble gas.
Noble gases
- Noble gases are unreactive because their outer shells are already full, so they do not need to bond.
Two methods
- Bonding involves either transferring electrons, which forms ionic bonds, or sharing electrons, which forms covalent bonds.
Section 2 of 4Ionic or Covalent?
The elements involved in a bond show which type of bonding will occur.
Ionic or Covalent?
Ionic
- Electrons are transferred from a metal to a non-metal, forming oppositely charged ions that are held by strong attraction.
Covalent
- Electrons are shared in pairs between non-metal atoms, so no ions are formed.
Metallic
- Metal atoms lose outer electrons, which move freely among the metal ions in a giant lattice.
Key difference
- In covalent bonding electrons are shared rather than transferred, which is why no ions are created.
| Feature | Ionic bonding | Covalent bonding |
|---|---|---|
| Elements involved | Metal and non-metal | Non-metal and non-metal |
| Electrons | Transferred | Shared in pairs |
| Particles formed | Ions | Molecules |
| Holding force | Electrostatic attraction between ions | Shared pairs of electrons |
Section 3 of 4Identifying the Bond Type
The type of bond can be worked out from the position of the elements in the periodic table.
1
Identify the elements involved; a metal combined with a non-metal usually forms an ionic bond.
2
If both elements are non-metals, the atoms usually share electrons in covalent bonds.
3
If both elements are metals, the bonding is metallic, with outer electrons free to move between the ions.
4
Remember that every atom in a bond is aiming for the stable electron arrangement of a noble gas.
Section 4 of 4Exam Checklist & Tips
2.1.1 – Key Points for the Exam
- Compound A substance formed from two or more elements chemically combined.
- Ionic bond The bond formed by the transfer of electrons from a metal atom to a non-metal atom.
- Covalent bond The bond formed when two non-metal atoms share a pair of electrons.
- Metallic bond The attraction between metal ions and the delocalised electrons around them.
- Full outer shell The stable electron arrangement that atoms aim to achieve through bonding.
Common Mistakes
- Saying that atoms bond to become full of electrons; they bond to achieve a full outer shell.
- Stating that a covalent bond transfers electrons, which describes ionic bonding instead.
- Assuming every compound of a metal is covalent; a metal and a non-metal normally form an ionic bond.
- Writing that noble gases form compounds easily; they are unreactive because their outer shells are full.