They are also known as the alkali metals.
They are lithium, sodium, potassium, rubidium, caesium and francium. They are very reactive because they have on electron in their outershell. They are soft.
As you go down the group, reactivity increases because the electrostatic attraction between the nucleus and the outershell decreases as it is further away. They also have lower melting and boiling points and higher relative atomic masses.
When group 1 metals are put in water they react vigorously and the more reactive the metal the more voilent the reaction. Lithium, sodium and potassium float and fizz vigorously. They produce hydrogen gas. Potassium react so vigorously that is ignites and burns with a lilac flame. The prdocue a hydroxide when they react with water.
They also react with chlorine gas to produce metal chlorides (white salts).