(a) Write the symbol for an ion with 8 protons, 9 neutrons, and 10 electrons.

(b) Write the symbol for an ion with 20 protons, 20 neutrons, and 18 electrons.

Strategy

Determine the identity of the atom from the number of protons and sum the number of protons and neutrons to get the mass number. Th e charge is determined by the numbers of protons and electrons: charge = the number of protons = the number of electrons. If more protons are present, the charge will be positive, and if more electrons are present, the charge will be negative.