Determine the number of protons and neutrons in plutonium-239 and enter its symbol in the form azx.

number of protons: 94
number of neutrons: 145

  239
       Pu
   94

Explanation:

1) The atomic number, Z, of plutonium is Z = 94, i.e plutonium 94 protons

2) Plutoniun-239 is the isotope with mass number 239.

3) Mass number = number of protons + number of neutrons =>

number of neutrons = mass number - number of protons = 239 - 94 = 145

4) The notation requires that you indicate the symbol of the element with the atomic number (number of protons) and the mass number.

You put the mass number as a superscript at the left side of the symbol and the atomic number as subscript to the left of the symbol.

So, in this case the symbol is Pu, the superscript to the left is 239 and the subscript to the left is 94.

  239
       Pu
   94

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