The Group 1 elements are reactive metals that are soft solids at room temperature (they have low melting and boiling points). The m.p's and b.p's decrease going down the group and the reactivity increases. They have low densities, so Li, Na and K float on water.
They all react readily with air and water. With water they produce H gas and a metal hydroxide (e.g. 2Li (s) + 2H2O (l) --> 2LiOH (aq) + H2 (g))
They react with the halogens to form salts that are white or colourless crystals (e.g. 2Na (s) + Cl2 (g) --> NaCl (s))
They all have one electron in their outer shell which they lost in reaction to form ionic compounds in which their ions have a single positive charge (e.g. K+)
Reactivity increases going down Group 1 because the outer electron is less strongly attracted to the nucleus so it is lost more easily.
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