The elements can be broadly divided into metals, nonmetals, and semimetals. Some of the groups have widely used common names, including the alkali metals (group 1) and the alkaline earth metals (group 2) on the far left, and the halogens (group 17) and the noble gases (group 18) on the far right. Elements that exhibit similar chemistry appear in vertical columns called groups (numbered 1–18 from left to right) the seven horizontal rows are called periods. The periodic table is an arrangement of the elements in order of increasing atomic number. As expected, semimetals exhibit properties intermediate between metals and nonmetals. Most solid nonmetals are brittle, so they break into small pieces when hit with a hammer or pulled into a wire. Nonmetals can be gases (such as chlorine), liquids (such as bromine), or solids (such as iodine) at room temperature and pressure. Nonmetals, in contrast, are generally poor conductors of heat and electricity and are not lustrous. Of the metals, only mercury is a liquid at room temperature and pressure all the rest are solids. The vast majority of the known elements are metals. Metals-such as copper or gold-are good conductors of electricity and heat they can be pulled into wires because they are ductile they can be hammered or pressed into thin sheets or foils because they are malleable and most have a shiny appearance, so they are lustrous. The distinction between metals and nonmetals is one of the most fundamental in chemistry. As you might expect, elements colored in gold that lie along the diagonal line exhibit properties intermediate between metals and nonmetals they are called semimetals. The heavy orange zigzag line running diagonally from the upper left to the lower right through groups 13–16 in divides the elements into metals (in blue, below and to the left of the line) and nonmetals (in bronze, above and to the right of the line). The semimetals lie along a diagonal line separating the metals and nonmetals. The metals are on the bottom left in the periodic table, and the nonmetals are at the top right. The Arabic numbering system is the most widely accepted today.\) The Periodic Table Showing the Elements in Order of Increasing Z Many periodic tables include both Roman and Arabic numbers.
Alkaline Earth Metals: Group 2 (IIA) - 2 valence electrons.Alkali Metals: Group 1 (IA) - 1 valence electron.Many chemists and chemistry textbooks recognize five main families:Īnother common method of categorization recognizes nine element families: However, there are different ways of categorizing elements into families. Because element properties are largely determined by the behavior of valence electrons, families and groups may be the same. Element groups, on the other hand, are collections of elements categorized according to similar properties. The characteristics of the elements in these families are determined primarily by the number of electrons in the outer energy shell.
Elements are classified into families because the three main categories of elements (metals, nonmetals, and semimetals) are very broad. Element families are indicated by numbers located at the top of the periodic table.Īn element family is a set of elements sharing common properties.