## Chemistry (7th Edition)

("P" = Number of protons; "N" = Number of neutrons) 1. Number of protons: $P = Z$ (Atomic number) (Periodic table top number); ** Use a periodic table to determine each atomic number. (a) 13 (b) 16 (c) 30 (d) 82 2. Number of neutrons: Each proton and neutron is responsible for 1 unit of mass: $P + N = A$ ("A" is the top left number) Therefore: $N = A - P$ (a) $N = 27 - 13 = 14$ (b) $N = 32 - 16 = 16$ (c) $N = 64 - 30 = 34$ (d) $N = 207 - 82 = 125$