Ion Formation
Chemistry: Edexcel IGCSE, topic 6.1.6
Formation of Ions
We can predict the charge of atoms from the periodic table based on the group number.
Group 1
- Group 1 atoms have 1 electron in the outer shell. They can lose this electron to have a full outer shell.
- The atom then has 1 less negative electron than the number of positive protons. The ion becomes positive by 1.
Group 2
- Group 2 atoms have 2 electrons in the outer shell. They can lose these two electrons to have a full outer shell.
- The atom then has 2 less negative electrons than the number of positive protons. The ion becomes positive by 2.
Group 6
- Group 6 atoms have 6 electrons in the outer shell. They can gain 2 electrons to have a full outer shell.
- The atom then has 2 more negative electrons than the number of positive protons. The ion becomes negative by 2.
Group 7
- Group 7 atoms have 7 electrons in the outer shell. They can gain 1 electron to have a full outer shell.
- The atom then has 1 more negative electron than the number of positive protons. The ion becomes negative by 1.
Test yourself on Ion Formation
How many electrons will a group 2 atom lose to become an ion with a full outer shell?
How many electrons must a group 7 atom gain to become an ion with a full outer shell?