Sodium
sodium!
Nitrogen gas is stable. However there are nitrogen compounds that are reactive.
Being very reactive these elements react quickly and form compounds.
There is not an answer for this question. Potassium is highly reactive and forms a huge variety of compounds.
Fluorine
Sodium is a soft, highly reactive metal element. As a pure element it will react violently with water, producing a highly basic solution of sodium hydroxide. By contrast sodium forms very stable compounds. Some of the common ones include sodium chloride (table salt), sodium bicarbonate (baking soda), and sodium hypochlorite (bleach). Most sodium compounds are basic.
They are highly reactivated. they are reacting with other compounds.
CFC's are highly reactive compounds. They react with ozone and deplete it.
Ozone
Cerium is reactive but not highly reactive.
Fluorine forms a very large range of compounds since it is highly reactive (actually it is the most reactive element there is). Teflon and freon are both synthetic fluorine compounds. Fluorine salts such as potassium fluoride are used in toothpaste, or to fluoridate water.
CFC's gas is formed. These are highly reactive compounds that deplete ozone.