Atom Consists of several types of particles A number of which have mass and an electric charge The electron, proton, and neutron Nucleus contains protons and neutrons Outside of the nucleus we have electrons Electrically neutral in its normal state Each type of atom has its own unique pattern of electron orbits No two sets of orbits are exactly alike Atomic Nucleus Strong nuclear force Holds particles together Only capable of acting over distances about the size of the atomic nucleus Attractive force Stronger than the electrical force Physics