## Chemistry (4th Edition)

(a) $^{186}_{74}$W (b) $^{201}_{80}$Hg (c) $^{76}_{34}$Se (d) $^{239}_{94}$Pu
"$Z$" stands for the atomic number whereas "$A$" stands for the mass number. The atomic number is written as a subscript for the element symbol whereas the atomic mass is written as a superscript also to the left of the chemical symbol. (a) The atomic number given is for that of tungsten, W. The symbol for this isotope of tungsten is $^{186}_{74}$W. (b) The atomic number given is for that of mercury, Hg. The symbol for this isotope of mercury is $^{201}_{80}$Hg. (c) The atomic number given is for that of selenium, Se. The symbol for this isotope of selenium is $^{76}_{34}$Se. (d) The atomic number given is for that of plutonium, Pu. The symbol for this isotope of plutonium is $^{239}_{94}$Pu.