How to Write the Nuclear Symbol of an Atom

This worked problem demonstrates how to write nuclear symbol for an atom when given the number of protons and neutrons in an isotope.

Nuclear Symbol Problem

Write the nuclear symbol for an atom with 32 protons and 38 neutrons.

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Example Problem: Isotopes and Nuclear Symbols

By Anne Marie Helmenstine, Ph.D.

Solution

Use a Periodic Table to look up the element with an atomic number of 32. The atomic number indicates how many protons are in an element. The nuclear symbol indicates the composition of the nucleus. The atomic number (number of protons) is a subscript at the lower left of the symbol of the element. The mass number (sum of the protons and neutrons) is a superscript to the upper left of the element symbol. For example, the nuclear symbols of the element hydrogen are:

¹₁H, ²₁H, ³₁H

Pretend that the superscipts and subscripts line up on top of each other - they should do so in your homework problems, even though they don't in my computer example ;-)

Answer

The element with 32 protons is germanium, which has the symbol Ge.
The mass number is 32 + 38 = 70, so the nuclear symbol is (again, pretend the superscripts and subscripts line up):

⁷⁰₃₂Ge