Isotopes

The chemical symbol for carbon

The full chemical symbol for an element shows its mass number at the top and atomic number at the bottom. Here is the full symbol for an isotope of carbon, carbon-12 or ¹²C:

It tells us that a carbon atom has:

• Six protons (because its proton number, at the bottom, is 6)
• Six electrons (because the number of protons and electrons in…