According to, "An atom consists of a small, dense, positively charged nucleus surrounded by electrons that whirl about it in orbits, forming a cloud of charge." In a broad sense of the term, electrons are e... More » Science Physics Particle Physics

To find the number of electrons an element has, locate it on the periodic table of elements, find the atomic number, and note the number of protons; because atoms are naturally electrically neutral, the protons and elect... More »

To find the valence electrons in an atom, identify what group the element is in. An element in group 1A has 1 valence electron. For example, Li is in group 1A, so that means it has one valence electron. If the element is... More »

Niels Bohr discovered that the energy levels of electrons distinct and that they revolve in orbits around the nucleus. Additionally, he discovered that the electrons could jump from one orbit to another. More » Science Physics Particle Physics

A Bohr diagram shows the distribution of an atom's electrons among different energy levels, or electron shells. Each diagram also features the number of protons and neutrons in the atom's nucleus. More »

Rutherford’s atomic theory was that an atom had a central positive nucleus with negative electrons orbiting it. He developed this theory with his gold foil experiment. More »

The idea of electron shells was developed by Niels Bohr in his 1913 model of the atom, which places electrons into stable orbits around the nucleus. The Bohr model was a modification of the Rutherford model, which did no... More »