Chemical compound
Substance of multiple elements bonded in fixed proportions.
A chemical compound is a chemical substance composed of many identical molecules containing atoms from more than one chemical element held together by chemical bonds. Molecules consisting of atoms of only one element are not compounds. Compounds can be transformed into different substances by chemical reactions, which may break or form bonds. There are four major types: molecular compounds (covalent bonds), ionic compounds (ionic bonds), intermetallic compounds (metallic bonds), and coordination complexes (coordinate covalent bonds). Non-stoichiometric compounds form a disputed marginal case.
- types
- molecular, ionic, intermetallic, coordination complexes
- defining feature
- atoms from more than one element in fixed stoichiometric proportion
- identifier
- CAS number assigned by Chemical Abstracts Service
Lore & Background
Boyle used the idea of corpuscles—or 'atomes'—to explain how a limited number of elements could combine into a vast number of compounds. He noted that quicksilver could be transformed into various compounds and then recovered unchanged, illustrating the distinction between element and compound.
Reader's Guide
The modern definition requires a fixed stoichiometric proportion of two or more types of atoms. Chemical compounds have a unique chemical structure held together by chemical bonds, and many have a CAS number. Non-stoichiometric compounds, where proportions are reproducible but not integral, are a disputed marginal case. The distinction between compound and mixture has historically been unclear, but the element-compound distinction remains central.
Did You Know?
- A molecule consisting of atoms of only one element is not a compound.
- Non-stoichiometric compounds form a disputed marginal case.
Frequently Asked Questions
What is a Chemical Compound?
A chemical compound is a substance built from identical molecules, each containing atoms of two or more different elements locked together by chemical bonds. It represents the next level of matter beyond single-element substances.
What separates a Chemical Compound from a pure element?
The defining rule is that every molecule in a compound must include atoms of more than one element in a fixed stoichiometric ratio. A collection of atoms from only one element, however bonded, simply does not qualify as a compound.
What types of Chemical Compounds exist?
Four major families are recognized: molecular compounds (covalent bonds), ionic compounds (ionic bonds), intermetallic compounds (metallic bonds), and coordination complexes (coordinate covalent bonds). Non-stoichiometric compounds occupy a disputed marginal category outside these four.
How is a Chemical Compound uniquely identified?
Each recognized compound is assigned a CAS (Chemical Abstracts Service) number, which serves as its universal registry identifier across the chemical literature and databases.
What happens to a Chemical Compound during a chemical reaction?
A compound can be broken apart or reassembled into entirely new substances when its existing bonds are broken and new ones form. This bond-breaking-and-forming process is the core mechanism by which chemistry converts one set of compounds into another.
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