By Matthew Perdue Updated Mar 24, 2022

Atoms consist of three fundamental particles: protons, neutrons, and electrons. The nucleus contains protons (positive) and neutrons (neutral). Electrons orbit the nucleus carrying a negative charge. In a neutral atom the number of protons equals the number of electrons, resulting in no net charge. An ion is an atom that has gained or lost one or more electrons, giving it a positive or negative charge.

Step 1 – Determine the Net Charge

The net charge of an atom equals the number of protons minus the number of electrons. The proton count is the atomic number (Z) found on the periodic table. The electron count can be calculated as Z − charge. For example, a calcium ion that has lost two electrons has a charge of +2, so its electron count is 20 – 2 = 18.

Step 2 – Write the Symbol with Its Charge

When an element carries a net charge, its chemical symbol must include the charge as a superscript. Sodium cations are written as Na⁺ and chloride anions as Cl^–. In HTML, you can use the <sup> tag for the superscript.

Step 3 – Classify the Ion

A positively charged ion is called a cation; a negatively charged ion is called an anion. For instance, Na⁺ is a cation and Cl^– is an anion.

TL;DR

If an element’s symbol appears without a superscript charge, it is neutral.