Fig3_1 The helium atom

Fig3_1 The helium atom

Fig. 3.1 . An atom of helium contains two electrons that swarm about the atomís nuclear center in a cloud of largely empty space. The shading shows that the electrons can be anywhere, but are most likely to be found near the center of the atom. The magnified nucleus of the helium atom consists of two protons and two neutrons bound together by a strong nuclear force. The nucleus and each of its four particles are spherically symmetric. The size of the helium nucleus is about 1 fermi, or 1 fm, which is equivalent to 10-15 m. The atom is about 100,000 times bigger than the nucleus, with an atom size of about 105 fm or 10-10 m.

Copyright 2010, Professor Kenneth R. Lang, Tufts University