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Beryllium is the fourth element, and has four protons (red) in its nucleus, along with four neutrons (blue). Beryllium has four electrons, and each of its orbitals can hold a maximum of two. Orbitals are filled from the lowest energy (nearest the nucleus) first, so there are two electrons in the inner 1s orbital, and two in the higher energy 2s orbital (green spheres). For clarity, solid lines show the paths of the electrons. In reality, electrons can be found anywhere, and the shape of each orbital is based only on where it is most likely to be found