Which statement is true of covalent bonds?
they form when atoms lose electrons.
they form when atoms gain electrons.
the form when electrons are shared.
they form when ions are attracted to each other.

the ozone layer acts as a filter for the shorter wavelength and highly hazardous ultraviolet radiation (uvr) from the sun, protecting life on earth from its potentially harmful effects. when the sky is clear, there is an inverse relationship between stratospheric ozone and solar uvr measured at the earth's surface.

it is stable as it is in group 0 which have full outer shells of electrons