Plutonium-239 is used in nuclear bombs, here 239 is its mass number. For an atom, mass number is equal to sum of number of protons and neutrons.
Thus,
A=n+p=239...... (1)
From periodic table, the atomic number of plutonium is 94 which is equal to number of electron and proton in an atom.
Thus,
Z=p=94
Putting the value of p in equation (1)
n=239-94=145
The symbol is as follows:
[tex]_{Z}^{A}\textrm{X}[/tex]
Here, Z is atomic number, A is mass number and X is atom symbol thus, symbol for plutonium will be:
[tex]_{94}^{239}\textrm{Pu}[/tex]
Therefore, number of protons, neutrons and symbol is 94, 145 and [tex]_{94}^{239}\textrm{Pu}[/tex]respectively.
