How To Find the Symbol of an Ion

Worked Chemistry Problem

You can find the symbol for an ion if you know how many protons and electrons it has.
You can find the symbol for an ion if you know how many protons and electrons it has. Jason Reed, Getty Images

This worked chemistry problem demonstrates how to determine the symbol for the ion when given the number of protons and electrons.

Problem

Give the symbol of an ion which has 10 e- and 7 p+.

Solution

The notation e- refers to electrons and p+ refers to protons. The number of protons is an element's atomic number. Use the Periodic Table to find the element with an atomic number of 7. This element is nitrogen, which has the symbol N.

The problem states that there are more electrons than protons, so we know the ion has a negative net charge. Determine the net charge by looking at the difference in the number of protons and electrons: 10 - 7 = 3 more electrons than protons, or a 3- charge.

Answer

N3-