A chemical compound is a substance composed of two or more different types of atoms in a fixed stoichiometric proportion. The atoms are held together by chemical bonds, which can be covalent, ionic, metallic, or coordinate covalent. A molecule consisting of atoms of only one element is not a compound.
Chemical compounds can be transformed into different substances by chemical reactions, which may involve interactions with other substances. In this process, bonds between atoms may be broken and/or new bonds formed. There are four major types of compounds, distinguished by how the constituent atoms are bonded together.
– Molecular compounds are held together by covalent bonds. Examples include water (H2O), carbon dioxide (CO2), and methane (CH4).
– Ionic compounds are held together by ionic bonds. Examples include sodium chloride (NaCl), calcium carbonate (CaCO3), and magnesium oxide (MgO).
– Intermetallic compounds are held together by metallic bonds. Examples include brass (CuZn), bronze (CuSn), and steel (FeC).
– Coordination complexes are held together by coordinate covalent bonds. Examples include hemoglobin, chlorophyll, and vitamin B12.
A chemical formula specifies the number of atoms of each element in a compound molecule, using the standard chemical symbols with numerical subscripts. Many chemical compounds have a unique CAS number identifier assigned by the Chemical Abstracts Service. Globally, more than 350,000 chemical compounds (including mixtures of chemicals) have been registered for production and use.
The concept of a chemical compound has been in use since at least 1724, when the English minister and logician Isaac Watts used it in his Logick. The term “compound” has a meaning similar to the modern one. Among substances, some are called simple, some are compound. Simple substances are usually called elements, of which all other bodies are compounded. Elements are such substances as cannot be resolved, or reduced, into two or more substances of different kinds.
In conclusion, a chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. It can be transformed into a different substance by a chemical reaction, which may involve interactions with other substances. There are four major types of compounds, distinguished by how the constituent atoms are bonded together. A chemical formula specifies the number of atoms of each element in a compound molecule. Many chemical compounds have a unique CAS number identifier assigned by the Chemical Abstracts Service..