Why does the reactivity of group 1 elements increase as you go down the group?

Group 1 metals all have one electron in their outer shell. When they react they form positive metal ions by losing this electron. Since there is only one electron to lose, group 1 metals are all extrememely reactive. The reactivity of group 1 metals increases as you go down the group because: 1) The atomic radius increases. The atom is held together by strong electrostatic forces of attraction between the positive protons in the nucleus and negative electrons. As you go down the group, the outer shell electron is further away from the positive nucleus. This means that the electrostatic forces of attraction between the outer shell electron and the nucleus are weaker and therefore it takes less energy for the electron to be lost. 2) There are more inner electrons which repel the outer shell electron. As you go down the group, there are more inner electrons. These repel the outer shell electron (like charges repel) therefore pushing it away. This means that it takes less energy to remove this electron.