- When an alkali metal atom reacts, it loses its valence electron to form a positively charged ion. Example
- As we go down the group from one element down to the next, the atomic radius gets bigger due to an extra filled electron shell.
- The valence electron is further and further from the nucleus. Thus the attraction force between the nucleus and the valence electron become weaker and weaker.
- This causes the valence electron is easier to be released to form an ion when the atom takes part in a reaction.
Li → Li+ + e
Na → Na+ + e
K → K+ + e