The charge that alkali metal form when they involve in a chemical reaction with non metals is 1+
Explanation
Metals react by losing electron to form a positively charged ion.
Alkali metal has 1 electron in outermost sub shell which is donated when they react with non metals to form ions with a charge of 1+.
For example sodium (Na) metal with [Ne] 3S¹ electron configuration donate the 1 electron in outermost subshell (3S) to form Na⁺ ion.