An atom is comprised of a central portion called a nucleus that contains protons and neutrons. Electrons orbit the nucleus and are typically found in a one-to-one ratio with protons. Different stable atomic configuration... More »

The Bohr model of the hydrogen atom consists of a heavy proton orbited by an electron. It's best described as like a planet orbiting a star. Instead of gravity providing the attractive force to the system, the electron i... More »

A molecule composed of two hydrogen atoms and one oxygen atom is a molecule of water. The structure of water is written as H20, which signifies that two hydrogen (H) atoms and one oxygen (O) atom make up the molecule. More »

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The compact, positively-charged nucleus of an atom contains two main types of subatomic particles: protons and neutrons. Orbiting the atom's nucleus are negatively-charged subatomic particles called electrons. The mass o... More »

Atoms become radioactive when they have an excess of protons or neutrons in the nucleus, leading to unbalanced internal forces, which the atom balances by emitting radiation. Atoms with a different amount of neutrons or ... More »

The subatomic particles of protons and neutrons are found in the nucleus of an atom. Protons are particles with a positive charge, while neutrons have no charge. Electrons, which have a negative charge, are particles tha... More »

The number next to isotopes signifies the sum of the number of protons plus the number of neutrons in the nucleus of an atom. For a particular element, the number of protons never changes, but the number of neutrons can ... More »