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Two parallel lines between atoms, representing a shared double bond.
Also known as: Two lines between atoms
Sometimes confused with: Equals sign chemistry
Two parallel lines between atoms mean a double bond — four shared electrons. The count of lines is the count of electron pairs, which makes the notation arithmetic rather than symbolic.
Represents a covalent double bond: two shared pairs of electrons between the same two atoms.
Contexts: Laboratory
Counts electron pairs by lines, so one line is a single bond, two a double and three a triple — arithmetic rather than symbolism.
Contexts: Laboratory
Is not an equals sign despite being drawn identically, and the two are distinguished only by whether atoms or quantities sit either side.
Contexts: Mathematics, Laboratory
Two short straight lines of equal length drawn parallel and close together, joining two atoms in a structural formula.
Drawn identically; only what sits either side distinguishes a bond from an equality.