## Introductory Chemistry (5th Edition)

Plutonium-239 has 94 protons and 145 neutrons. $$^{239}_{94}Pu$$
1. As its name says, plutonium-239 has a mass number of 239. A = 239 2. Using a periodic table, we can see that for plutonium: Z = 94 = number of protons Number of neutrons = A - Z = 239 - 94 = 145 3. Knowing the value of A and Z (239 and 94): $$^{239}_{94}Pu$$