Atom to the positively charged nucleus by the attraction created from opposite electric charges. If an atom has more or fewer electrons than its atomic number, then it becomes respectively negatively or positively charged as a whole; a charged atom is called an ion. Electrons have been known since the late 19th century, mostly thanks to J.J. Thomson; see history of subatomic physics for details. Protons have a positive charge and a mass 1,836 times that of the electron, at . The number of protons in an atom is called its atomic number. Ernest Rutherford (1919) observed that nitrogen under alpha-particle
A Is for Atom A Is for Atom A Is for Atom is a 14-minute 1953 promotional animated short documentary film created by John Sutherland and sponsored by General Electric (GE). It is now in the public domain. The short explains what an atom is, how nuclear energy is released from certain kinds of atoms, the peacetime uses of nuclear power, and the by-products of nuclear fission. It is Sutherland's most-decorated film, having won numerous honors at film festivals. "A is for Atom" was re-released by General Electric in 1964. John Sutherland Studios was contracted by GE to modernize the film. Changes include included