Animation of an atom Check this out! Atoms Family Phantom's Portrait Parlor for more information about atoms and elements! Chem Time A Clock with Chemical Elements In the Chem Time clock, the numbers have been replaced by the symbols of the corresponding element. Try making your own using the 24-hour clock.

Atoms are the smallest subdivision of matter that retain the characteristics of the elements. They consist of a very small, massive nucleus composed of protons and neutrons surrounded by a much larger region of circling electrons. Atoms resemble a miniature solar system. At the center, corresponding to the Sun, is the nucleus which is made up of protons and neutrons. Proton have a positive charge; the neutron, as the name implies, is electrically neutral. Each electron, which, like a planet of the solar system, moves in an orbit around the nucleus, carries a negative charge. Since the atom as a whole is electrically neutral, there must be as many electrons as protons. The basic difference between atoms of different elements is due to the electrical charge of the nucleus, which in turn, is related to the number of protons. This number (which is equal to the number of electrons) is called the atomic number. The elements in the periodic table are arranged according to increasing atomic number. (More about the periodic table.) The chemical properties of the elements depend on how the electrons are arranged around the nucleus. Electrons are considered to be arranged about the nucleus in energy levels, or shells. The number of shells for each atom range from 1 to 7. In the periodic table the elements are arranged in groups where the number of electrons in the outermost shell is the same for the atoms of each element in a group and is equal to the group number. It is the number of these outer shell (valence) electrons that determines the chemical properties of an element.

Crystal Chemistry