Ions

• Ions are charged particles.
• Ions can be single atoms (e.g. Na+) or groups of atoms (e.g. NO3-)
• Anions (negative ions) form when atoms gain electrons
• Cations (positive ions) form when atom lose electrons
• The number of electrons lost / gained is the same as the charge on the ion. (e.g. 3 electrons lost = 3+ charge)
• Groups 1, 2 and 3 are all metals
• Metals lose electrons to form cations. (positive ions)
• Groups 5, 6 and 7 are all non-metals
• Non-metals gain electrons to form anions. (negative ions)
• Elements in the same group all have the same number of outer shell electrons
• Group 1 elements form 1+ ions
• Group 2 elements form 2+ ions
• Group 3 elements form 3+ ions
• Group 5 elements form 3- ions
• Group 6 form 2- ions
• Group 7 form 3- ions