In nuclear physics, "magic numbers" identify specific numbers of protons or neutrons that lead to especially stable nuclei.

The atom with eight protons in its nucleus (atomic number 8) is oxygen. Image Periodic Table of Energy Levels. Download Image. Each energy level holds a certain number of electrons before electrons go ...

Magic numbers" in nuclear physics identify specific numbers of protons or neutrons that lead to especially stable nuclei.

Let's try an example: We can choose selenium, which has an atomic number of 34, meaning there are 34 total electrons in a neutral atom of selenium. This non-metal resides in Period 4, Group 6A.

Because neutral atoms in the periodic table have the same number of electrons as protons, the atom must have 8 protons. The number of protons is the same as the atomic number, so the atom is oxygen.