Why are the members of group IA called alkali metals

The alkali metals are so named because when they react with water they form alkalies. Alkalies are hydroxide compounds of these elements, such as sodium hydroxide and potassium hydroxide. ... Alkalies react with acids to form salts.

Explanation:

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.

it is stable as it is in group 0 which have full outer shells of electrons