By R.L. Cultrona | Updated March 24, 2022

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The periodic table is the definitive reference for every element on Earth, detailing their atomic structure and relationships. By consulting this table, you can determine the number of protons, electrons, and neutrons that compose each atom.

Step 1: Select an Element

Choose the element you wish to analyze. In this example, we’ll use gold, whose chemical symbol is Au and is positioned in period 6.

Step 2: Identify the Atomic Number and Mass

Locate the atomic number (Z) and the atomic mass (A). The atomic number appears in the upper left corner of the element’s box, while the atomic mass is listed just below the symbol. For gold, Z = 79 and A = 196.966569. Round the mass to the nearest whole number (A ≈ 197).

Step 3: Calculate Neutrons

Neutrons = A – Z. Because the atomic mass represents the total number of nucleons (protons + neutrons), subtracting the number of protons (equal to the atomic number) yields the neutron count. For gold: 197 – 79 = 118 neutrons.

What You’ll Need

• A periodic table (physical or digital)
• A calculator or mental math for quick subtraction

TL;DR

Use the periodic table to find the neutron count for any element. The atomic number equals the number of protons—and, in a neutral atom, the number of electrons.