Forming Ions
How are ions formed?
- As a general rule, metals are on the left of the Periodic Table and non-metals are on the right-hand side
- Ionic bonds involve the transfer of electrons from a metallic element to a non-metallic element
- Transferring electrons usually leaves the metal and the non-metal with a full outer shell
- Metals lose electrons from their valence shell forming positively charged cations
How a sodium atom forms a sodium ion
Forming cations by the removal of electrons from metals
- Non-metal atoms gain electrons forming negatively charged anions
How a chlorine atom forms a chloride ion
Forming anions by the addition of electrons to non-metals
- Once the atoms become ions, their electronic configurations are the same as a noble gas.
- A sodium ion (Na+) has the same electronic configuration as neon: [2,8]
- A chloride ion (Cl-) also has the same electronic configuration as argon: [2,8,8]
Exam Tip
Metals usually lose all electrons from their outer shell to become positive ions or cations.
You can make use of the groups on the periodic table to work out how many electrons an atom is likely to lose or gain by looking at the group an atom belongs to.
