Chlorine has an atomic number of 17. it often forms an ion by gaining 1 electron. what would its charge be?

The charge would be -1.

Explanation:

The atomic number refers to the number of protons an atom has. Chlorine is electrically neutral, so it has the same  number of positive charges (protons) than negative charges (electrons). Therefore, chlorine has 17 protons and 17 electrons. When it gains 1 electron, it will have an excess of one negative charge, so the charge of the ion will be -1, forming Cl⁻.

dynamic equilibrium is the answer.

they it depends on if one believes about radioactivity, they make a geiger counter beep but maybe it was going to beep anyway electronics do wierd things all the time or it was programmed to beep near certain metals.