Question

how do good and bad ozone form?

Explanation:

Good ozone (stratospheric ozone) forms when ultraviolet (UV) radiation from the sun breaks apart an oxygen - molecule ($O_2$) into two oxygen atoms. Each of these oxygen atoms then combines with an $O_2$ molecule to form ozone ($O_3$). Bad ozone (tropospheric ozone) is a secondary pollutant. It forms through chemical reactions between nitrogen oxides ($NO_x$) and volatile organic compounds (VOCs) in the presence of sunlight.

Answer:

Good ozone forms when UV radiation breaks $O_2$ and oxygen atoms combine with $O_2$ to make $O_3$. Bad ozone forms from reactions between $NO_x$, VOCs and sunlight.