Passage VI

An atom has a nucleus, which consists of protons (positively charged particles) and neutrons (uncharged particles), surrounded by one or more electrons (negatively charged particles) which move in orbits (see Figure 1).

Table 1 contains data for several neutral and charged atoms containing only one electron. Table 1 includes the number of protons (Z); the identification of the initial orbit (n); the radius of the orbit (r); the energy (l, in electron volts, or eV) to remove an electron from the atom; and the energy (E) of a photon emitted when an electron falls from its initial orbit to the orbit where n = 1.