Lecture 4 – Group I: Alkali Metals

Group I: Alkali Metals

1. Group I metals are alkali metals with 1 electron in their valence shell.
2. They form a family of soft metals that can be cut with a knife like butter.
3. The have low densities and can float over water.
4. Their melting point decreases down the group.
5. Reactivity of Alkali metals increases down the group.
• This is because, as the atomic number increases, the radius of the atom increases, pushing the valence shell and hence the valence electron further away from the nucleus. The valence electron is loosely attached to the atom by a weak electrostatic force from the nucleus. Therefore, it is easy for the atom to lose its loosely bonded valence electron. And hence reactivity of Group I elements increases down the Group.
6. They form +1 positive ions by losing their loosely bonded valence electron.
7. They react with water to form metal hydroxides and Hydrogen gas.

8. They react with halogens of Group VII to form salts.

9. They undergo displacement reactions, where a less reactive metal is displaced by a more reactive metal in its salt solution.