Halogens Group 7A; very reactive non-metals; gain 1 valence electron to become negatively charged

Group 2A; slightly less reactive metals; lose their 2 valence electrons to become positively charged

Group 8A; non-reactive non-metals; do not lose or gain valence electrons, because they already have 2 or 8 valence electrons

Group 1A; very reactive metals; lose their 1 valence electron to become positively charged

it would be a gas formation

chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. these processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. some reactions produce heat and are called exothermic reactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. understanding chemical changes is a major part of the science of chemistry.