Chemical compound
A chemical compound is a substance formed when two or more elements are chemically bonded together. Elements are the simplest forms of matter, consisting of only one type of atom and cannot be broken down into simpler substances. Each element is represented on the periodic table and identified by a unique symbol and atomic number. When elements combine to form compounds, they exhibit distinct properties that differ from those of the individual elements. Common examples of chemical compounds include water (H₂O), sugar, salt (sodium chloride), and vinegar. The bonds that hold these compounds together can be covalent, where atoms share electrons, or ionic, where electrons are transferred between atoms. Chemical compounds can be classified in various ways, including organic versus inorganic and by their bonding types. Additionally, naming conventions for chemical compounds are guided by specific rules that help identify the elements and their quantities in a compound, such as using prefixes to denote the number of atoms involved. Understanding chemical compounds is essential for studying chemistry and its applications in various fields.
Chemical compound
A chemical compound is a substance formed when two or more elements bond. An element is a primary component of matter. It contains only one type of atom and cannot be broken down into a simpler substance. Elements are listed on the periodic table. A chemical compound is a unique substance with properties not found in its elements. It may contain two elements or millions of elements. Water, sugar, salt, and vinegar are common chemical compounds. Scientists have discovered millions of chemical compounds and believe that many more exist.
Elements
Chemical compounds consist of one or more elements. An element contains only one type of atom. All matter on Earth and in the universe is made of elements. As of 2024, scientists have discovered 118 elements, about 98 of which occur naturally in nature. Hydrogen, helium, and oxygen are the most common elements on Earth and in nature. All elements are listed on the periodic table, and each has a unique symbol, which may be a capital letter or a capital letter and a lowercase letter. For example, the symbols for hydrogen, helium, and oxygen are H, He, and O. Each element also has an atomic number, which is the number of protons found in the nucleus of an atom of that element. Hydrogen’s atomic number is one, helium’s is two, and oxygen’s is eight.
Some elements were discovered thousands of years ago. Copper (Cu), sulfur (S), silver (Ag), tin (Sn), antimony (Sb), gold (Au), mercury (Hg), and lead (Pb) were discovered in ancient times. The discovery of other elements is more recent. For example, darmstadtium (Ds) and roentgenium (Rg) were discovered in 1994.
Chemical Bonds
Chemical compounds form when elements are joined by chemical bonds. These bonds are very strong—so strong that they make the compound behave like a single substance. Atoms that are connected by chemical bonds are referred to as molecules.
Two main types of bonds create chemical compounds. Covalent bonds exist when atoms in a chemical compound share electrons. The atoms in hydrogen chloride, a chemical compound consisting of hydrogen and chlorine, have covalent bonds. Hydrogen chloride is a gas used to clean metals and make dyes and fertilizers.
Ionic bonds, the second main type of chemical bond, occur when electrons move from one atom to another. This happens because negatively and positively charged ions are attracted to each other. The atoms in sodium chloride, a chemical compound commonly known as table salt, have ionic bonds.
Names of Chemical Compounds
Scientists name chemical compounds using a set of rules. Note that the rules in this section are just an introduction. The rules for naming chemical compounds that contain many elements and chemical compounds of different types can be quite complex.
Naming a chemical compound that consists of one atom of each of two elements is easy. The first word is the name of the first element. The second word is the name of the second element along with the suffix -ide. For example, if oxygen was the second element in a chemical compound, it would be oxide. If chlorine was the second element, it would be chloride.
The naming convention becomes more complicated if the chemical compound contains more than one atom of an element. When this is the case, a prefix is added to the element’s name. This prefix indicates how many atoms of that element are in the chemical compound. These are the prefixes used:
Number of atoms: Prefix
1: mono- (only used on the second element)
2: di-
3: tri-
4: tetra-
5: penta-
6: hexa-
7: hepta-
8: octa-
9: nona-
10: deca-
Suppose a chemical compound consists of one atom of carbon and two atoms of oxygen. The first word in the name would be carbon. Since only one atom of carbon is in the chemical compound, no prefix is needed. Since two atoms of oxygen are in the second compound, the prefix di- is used. Since oxygen is the second element, the suffix –ide is also used. The name of the chemical compound is carbon dioxide. The symbol of the chemical compound is CO2. Note that the subscript 2 is used to indicate that the compound contains two atoms of oxygen. The following are additional examples of the names of symbols of chemical compounds:
(1 carbon atom and 1 oxygen atom) carbon monoxide CO
(1 carbon atom and 4 chlorine atoms) carbon tetrachloride CCL4
(2 hydrogen atoms and 1 oxygen atom) dihydrogen monoxide H2O
Classification of Chemical Compounds
Chemical compounds can be classified in different ways. They can be classified by the type of bond, chemical or ionic. They can also be classified by an element within them. For example, oxides are chemical compounds that contain oxygen. Chemical compounds are often divided into two groups: organic and inorganic compounds. Organic compounds contain carbon and are typically part of living things. Carbohydrates, lipids (fats), and proteins are organic compounds. Inorganic compounds are all those that do not contain carbon. Sometimes chemical compounds are classified by their acidity, the level of acid within them. Compounds classified in this way may be grouped into acids and bases.
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