5.1: The Periodic Table Certain elemental properties become apparent in a survey of the periodic table as a whole. Every element can be classified as either a metal, a nonmetal, or a metalloid (or semi metal). A metal is a substance that is shiny, typically (but not always) silvery in color, and an excellent conductor of electricity and heat. Metals are also malleable (they can be beaten into thin sheets) and ductile (they can be drawn into thin wires). 5.2: Monotomic and Diatomic Elements Most elements exist with individual atoms as their basic unit. It is assumed that there is only one atom in a formula if there is no numerical subscript on the right side of an element’s symbol. There are many substances that exist as two or more atoms connected together so strongly that they behave as a single particle. There are seven elements that exist as diatomic molecules. 5.3: The Structure of Atoms Atoms are composed of three main subatomic particles: protons, neutrons, and electrons. Protons and neutrons are grouped together in the nucleus of an atom, while electrons orbit about the nucleus. 5.4: The Nuclei of Atoms Elements can be identified by their atomic number and mass number. Isotopes are atoms of the same element that have different masses. 5.5: Atomic Masses Atoms have a mass that is based largely on the number of protons and neutrons in their nucleus.