Lesson 3.4 Nonmetals and Metalloids

Life on Earth depends on many nonmetals. For example, carbon, nitrogen, phosphorus, hydrogen, and oxygen are all nonmetal elements found in your body’s DNA.

While many compounds made with nonmetals are essential to life, some nonmetals are poisonous and highly reactive. For example, if you breathed in pure oxygen, you would eventually get very sick.

Physical properties – a nonmetal is an element that lacks most of the properties of a metal. Except for hydrogen, the nonmetals are found on the right side of the periodic table. In general, most nonmetals are poor conductors of electric current and heat. Solid nonmetals tend to be dull and brittle. If you were to hit most solid nonmetals with a hammer, they would break or crumble into a powder.

Many nonmetals are gases at room temperature. The air you breathe contains mostly nitrogen and oxygen. Carbon, sulfur, and iodine are solids at room temperature. Bromine is the only nonmetal that is a liquid at room temperature.

Chemical properties – atoms of nonmetals usually gain or share electrons when they react with other atoms. When nonmetals and metals react, electrons move from the metal atoms to the nonmetal atoms. For example, when sodium and chlorine react to form table salt (NaCl), an electron moves from the sodium atom to the chlorine atom. https://www.youtube.com/watch?v=oZdQJi-UwYs sodium and chlorine video

Nonmetals can form compounds with other nonmetals, and when they do, they share their electrons to form bonds. When two or more atoms bond this way, they form a molecule.

Nonmetal families – the families containing nonmetals include the carbon family, the nitrogen family, the oxygen family, the halogen family, the noble gases, and hydrogen.

Carbon Family – in group 14, only carbon is a nonmetal. Carbon is extremely important due to its role in the chemistry of life – DNA, protein, and fats all contain carbon. Coal contains large amount of carbon, so does gasoline, and a diamond is pure carbon.

Nitrogen Family – Group 15, the nitrogen family contains 2 nonmetals: nitrogen and phosphorus. Nitrogen makes up about 78% of Earth’s atmosphere, and in nature, nitrogen exists as two nitrogen atoms bonded together. Nitrogen is a diatomic molecule; it is made up of two of the same atoms (N₂). In this form, it is not very reactive.

All living things need nitrogen, but most of them are unable to use nitrogen from the air. Certain kinds of bacteria can use the nitrogen in the air. Plants can then take in these nitrogen compounds formed by the bacteria in the soil and fertilizers.

Phosphorus is much more reactive than nitrogen, and is always found in compounds in nature.

Oxygen Family – Group 16 contains 3 nonmetals: oxygen, sulfur, and selenium. Oxygen is a gas at room temp, while sulfur and selenium are solids. You are using oxygen right now with every breath. Like nitrogen, oxygen (O₂) is a diatomic molecule. Oxygen is reactive, so it can combine with almost every other element. Sulfur is used to make rubber bands and automobile tires.

Halogen Family – Group 17 contains the nonmetals fluorine, chlorine, bromine, and iodine. They are known as the halogens, which means “salt forming.” Properties of astatine are unknown because it is extremely rare. All of the halogens are extremely reactive and dangerous. They react with almost every known substance, including water. Fluorine is the most reactive. Chlorine gas is extremely dangerous, but used in small amounts to kill bacteria. Though the halogen elements are dangerous, they form useful compounds. Fluorine compounds are found in toothpaste to prevent tooth decay.

Noble Gases - in group 18 are nonreactive. They do not gain, lose, or share electrons. Helium is used in balloons, and noble gases are also used in glowing electric lights.

Hydrogen – Alone in the upper left corner. The chemical properties of hydrogen are very different from those of other elements, so it cannot be grouped with a family. Hydrogen makes up 90% of the atoms in the universe. Stars contain massive amounts of hydrogen, but only makes up 1% of the mass of the Earth. It is rarely found on Earth as a pure element. Most hydrogen is contained with oxygen in water.

Metalloids – they have some properties of metals and some properties of nonmetals. All metalloids are solid at room temp. They are brittle, hard, and somewhat reactive. The most common metalloid is silicon. It is the main component in sand and glass (SiO₂). Boron is added to make glass heat-resistant.

A metalloid’s most useful property is the ability to conduct electric current and can be used to make semi-conductors in computer chips, solar panels and lasers. Semiconductors are substances that can conduct electric current under some conditions, but not always.