Although not the same as the sun and planets, an atom has a central core with electrons that travel around it.

Atoms are the building blocks of all matter. They can be divided into two major components, the center or nucleus and the orbiting electrons that surround—but do not touch—the nucleus. The nucleus has a positive electrostatic charge, while the electrons have a negative electrostatic charge. The nucleus can be further divided into its own component parts.

The Nucleus

The central nucleus, sometimes referred to as the core of the atom, is generally ball-shaped and consists of two types of particles, positively charged protons and electrically uncharged neutrons. It is the number of protons that determines what variety of element an atom will be. One proton makes hydrogen, two protons make helium, 11 protons make sodium and 82 protons make lead. Neutrons may vary in number and affect the weight of the atom. Weight variants are called isotopes.

The Electrons

Atoms, although they contain both negative and positive electrical charges, must have a total or net charge equal to zero. That means that the number of protons in an atom and the number of electrons are equal. The electrons travel around the nucleus in often unusually shaped, mathematically determined portions of space called orbitals.