Reactions and compounds

Back to Science main page

Sulfur and iron BEFORE mixing.

Sulfur and iron AFTER mixing and being heated.
The elements iron and sulfur combine chemically to form the compound iron sulfide

Chemical reactions produce new substances. Elements may react together to form compounds, because their atoms join to other atoms using chemical bonds.

For example, iron and sulfur (often spelt 'sulphur') react together to form a compound called iron sulfide (often spelt 'sulphide'), and sodium and oxygen react together to form sodium oxide.

The significance of electrons in bonding

Chemical bonds are produced by a change in position of outer electrons in the reacting atoms.

Bonds can form when:

  • electrons are transferred from one atom to another, so that one atom gives electrons and the other takes electrons, or
  • electrons are shared between two atoms.