Answer
(a) 13 protons and 14 neutrons
(b) 16 protons and 16 neutrons.
(c) 30 protons and 34 neutrons.
(d) 82 protons and 125 neutrons.
Work Step by Step
("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) $N = 207 - 82 = 125$
