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
Up An' Atom Up An' Atom Up An' Atom was the name of a B-29 Superfortress (B-29-36-MO 44-27304, Victor number 88) configured during World War II in the Silverplate project to carry an atomic bomb. Assigned to the 393d Bomb Squadron, 509th Composite Group, it was built at the Glenn L. Martin Aircraft Plant at Omaha, Nebraska, accepted by the Army Air Forces on April 3, 1945, and flown to Wendover Army Air Field, Utah, by its assigned crew B-10 (Capt. George W. Marquardt, Aircraft Commander). It departed Wendover for North Field, Tinian on June 11 and arrived on June 17. It was