Dear student,
Non-Metals react with oxygen to form a non-metal oxide which is acidic in nature.
Non Metals+Oxygen= Non-metal oxide + H20= acidic nature
S2+O2= SO2 +H20=H2SO3 (acid)
Simply, If an element forms a basic oxide, then the element will be a metal
If an element forms an acidic oxide, then the element will be a non-metal
Thank You