Nonmetal

Nonmetals are special kinds of elements in chemistry that do not have the usual properties of metals. Unlike metals, which are often shiny and good conductors of heat and electricity, nonmetals can be gases, like hydrogen, or solids, like iodine. They are usually lighter and do not conduct electricity well.

There are seventeen elements that are widely known as nonmetals, and six more elements called metalloids that are sometimes included in this group. Two of the lightest nonmetals, hydrogen and helium, make up about 98% of everything we can see in the universe. These elements are very important for life on Earth, forming much of our atmosphere, biosphere, crust, and oceans.

Nonmetals are used in many everyday things. They are important in electronics, helping make computers and phones work, and they play a role in processes like combustion, which is how things burn. Even though people have known about metals for thousands of years, scientists only started classifying nonmetals in the late 1700s. Today, we understand these elements help create many chemical compounds and alloys that we use in our world.

Definition and applicable elements

Unless otherwise noted, this article describes the stable form of an element at standard temperature and pressure (STP).

Nonmetallic chemical elements are elements that usually don’t have the typical qualities of metals, like shine, flexibility, or good ability to carry heat and electricity. Because of how their electrons are arranged band structure, they behave differently from metals.

Fourteen elements are almost always called nonmetals: Hydrogen, Nitrogen, Oxygen, Sulfur, Fluorine, Chlorine, Bromine, Iodine, Helium, Neon, Argon, Krypton, Xenon, and Radon. Some other elements, like Carbon, Phosphorus, and Selenium, are often grouped with nonmetals too, though they might also be called "metalloids".

General properties

Nonmetals are elements that lack typical metallic properties. They come in many forms, from colorless gases like hydrogen to shiny crystals like iodine. Most nonmetals are lighter and less dense than metals and usually do not conduct heat or electricity well.

About half of nonmetals are gases at normal temperatures and pressures, while most others are solids. The only liquid nonmetal is bromine. Nonmetals can vary widely in appearance, being colorless, colored, or even shiny. Their properties depend on their structure and how their atoms bond together. Some nonmetals can form different structures called allotropes, each with unique characteristics. For example, carbon can be found as graphite, diamond, or fullerenes, each having different physical properties.

Types

Main article: Nonmetal classification schemes

There are different ways scientists group nonmetals, and these groups can vary a lot. Some simple tables might only have a few groups, while more detailed ones can have up to seven. One common way to look at nonmetals starts from the right side of the periodic table and finds three main types.

The first group is the noble gases, which include helium, neon, argon, krypton, xenon, and radon. These gases are known for not reacting with other elements very easily. The second group is the halogen nonmetals, made up of fluorine, chlorine, bromine, and iodine. These elements are very reactive and often form compounds with metals. The third group is called "unclassified nonmetals" and includes hydrogen, carbon, nitrogen, oxygen, phosphorus, sulfur, and selenium. These elements don’t have a single common name but share some mixed properties. Sometimes, elements like boron, silicon, germanium, arsenic, antimony, and tellurium are also considered nonmetals because they have properties in between metals and nonmetals.

Each of these groups has its own special traits. Noble gases are colorless, smellless, and don’t catch fire. Halogens are very reactive and form strong bonds with metals. Unclassified nonmetals can act a bit like metals in some situations and like nonmetals in others, making them interesting to study.

Abundance, extraction, and uses

The abundance of elements in the universe comes from processes like nucleosynthesis and radioactive decay. Some nonmetal elements, like the noble gases, are less common in Earth's atmosphere than we might expect. For example, xenon is found in small amounts and might be stored deep within the Earth.

Five important nonmetals—hydrogen, carbon, nitrogen, oxygen, and silicon—make up most of Earth’s crust, water, air, and living things. Silicon and oxygen form strong structures called silicates, which help hold Earth's crust together.

Nonmetals are obtained from many places. Gases like hydrogen and oxygen are taken from natural gas and liquid air. Others, like chlorine, come from seawater. Many nonmetals are also found in solid ores and are mined from the Earth.

Nonmetals have many uses. Hydrogen can power fuel cells. Carbon is used in diamonds for jewelry and cutting tools, and as graphite for lubrication. Liquid nitrogen is a coolants. Oxygen is important for breathing and is used in welding and rocket fuels. Silicon is key in making electronics. Noble gases have special uses, like cooling and fire safety. Radon, though, can be a harmful indoor pollutant.

Taxonomical history

Medieval chemical philosophers mainly studied metals and rarely looked into nonmetallic minerals.

French chemist Antoine Lavoisier made big changes in chemistry. In 1789, he created the first modern list of chemical elements. He grouped the 33 known elements into four types: gases, metals, nonmetals, and earths. His work was very important and helped many people understand chemistry better.

Later scientists developed new ways to sort elements. In 1802, the term “metalloids” was used for elements that had some properties of metals and some of nonmetals. By the mid-1800s, scientists like Alphonse Dupasquier created new groupings for nonmetals, such as organogens and chloroides. These early ideas helped lead to the periodic table we know today.

Comparison of selected properties

See also § Physical

Physical properties are listed in loose order of ease of their determination.

See also § Chemical

Chemical properties are listed from general characteristics to more specific details.

† Hydrogen can also form alloy-like hydrides
‡ The labels low, moderate, high, and very high are arbitrarily based on the value spans listed in the table