## Physics for Scientists and Engineers: A Strategic Approach with Modern Physics (4th Edition)

(a) $^3H$ has 1 proton $^3H$ has 2 neutrons (b) $^{40}Ar$ has 18 protons $^{40}Ar$ has 22 neutrons (c) $^{40}Ca$ has 20 protons $^{40}Ca$ has 20 neutrons (d) $^{239}Pu$ has 94 protons $^{239}Pu$ has 145 neutrons
(a) $^3H$ has atomic number 1 $^3H$ has 1 proton Note that $3-1 = 2$ $^3H$ has 2 neutrons (b) $^{40}Ar$ has atomic number 18 $^{40}Ar$ has 18 protons Note that $40-18 = 22$ $^{40}Ar$ has 22 neutrons (c) $^{40}Ca$ has atomic number 20 $^{40}Ca$ has 20 protons Note that $40-20 = 20$ $^{40}Ca$ has 20 neutrons (d) $^{239}Pu$ has atomic number 94 $^{239}Pu$ has 94 protons Note that $239-94 = 145$ $^{239}Pu$ has 145 neutrons