This document discusses the properties of group 1 elements on the periodic table (alkali metals). It describes their physical properties such as increasing atomic radius and decreasing melting/boiling points down the group. Chemically, they are highly reactive and form ionic compounds by losing their single valence electron. Their reactivity increases down the group due to the greater atomic size and weaker hold of the outer electron. Safety precautions are needed when handling alkali metals due to their reactivity.