Properties of Nonmetals
A nonmetal is an elements that lacks most of the properties of a metal. Most nonmetals are poor conductors of electricity and heat and are reactive with other elements. Solid nonmetals are dull and brittle.
Physical properties Ten of the 16 nonmetals are gases at room temperature. The air you breathe is mostly a mixture os two nonmetals, nitrogen (N), and oxygen (O). Other nonmetals such as carbon (C), iodine (I), and sulfur (S), are solids at room temperature. Bromine (Br) is the only nonmetal that is liquid at room temperature. In general, the physical properties of nonmetals are the opposite of those of the metals. Nonmetals are also poor conductors of heat and electricity.
Chemical properties Most nonmetals are reactive, so they readily form compounds. In fact, fluorine (F) is the most reactive element known. Atoms of nonmetals usually gain or share electrons when they react with other atoms. When nonmetals and metal react, electrons move from the metal atoms to the nonmetal atoms. Many nonmetals can also form compounds with other nonmetals. The atoms share electrons and become bonded together into molecules.
Families of nonmetals
The Carbon Family Each element in the carbon family has atoms that can gain, lose, or share four electrons when reacting with other elements. What makes carbon especially important is its role in the chemistry of life. Compounds made of molecules containing long chains of carbon atoms are found in all living things. Most os the fuels that are burned to yield energy contain carbon. Coal, is mostly the element carbon.
The Nitrogen Family The nitrogen family contains two nonmetals, nitrogen and phosphorus. These nonmetals usually gain or share three electrons when reacting with other elements. The atmosphere is almost 80% nitrogen gas (N₂). Nitrogen is an example of an element that occurs in nature in the form of diatomic molecules, as N₂. A diatomic molecule consists of two atoms.
The Oxygen Family The oxygen family, contains three nonmetals - oxygen, sulfur, and selenium. These elements usually gain or share two electrons when reacting with other elements. Because oxygen is highly reactive, it can combine with almost every other elements. It also is the most abundant element in Earth's crust and the second-most abundant element in the atmosphere.
The Halogen Family Group 17 contains fluorine, chlorine, bromine, iodine, and astatine. These elements are also known as the halogens, which means "salt forming". A halogen atom typically gains or shares one electron when it reacts with other element. All of the halogens are highly reactive, and the uncombined elements are dangerous to humans. Many of the compounds that halogens form are quite useful.
The Noble Gases The elements in Group 18 are known as the noble gases. They do not ordinarily form compounds because atoms of noble gases do not usually gain, lose, or share electrons. As a result, the noble gases are usually unreactive. All the noble gases exist in Earth's atmosphere, but only in small amounts. Noble gases were not discovered until the late 1800s.
Hydrogen Alone in the upper left corner of the periodic table is hydrogen, the element with the simplest and smallest atoms. Each hydrogen atom has one proton and one electron. Some hydrogen atoms also have neutrons. The chemical properties of hydrogen differ very much from those of the other elements, it really cannot be grouped into a family.
The Metalloids
Along the border between nonmetals and metals are seven elements called metalloids. The metalloids have some characteristics of both metals and nonmetals. All are solids at room temperature. They are brittle, hard, and somewhat reactive. The most common metalloid is silicon (Si). The most useful property of the metalloids is their varying ability to conduct electricity. Whether or not a metalloid conducts electricity can depend on temperature, exposure to light, or the presence of small amounts os impurities. Semiconductors are substances that can conduct electricity under some conditions but not under other conditions.
