What Is a Chemical Formula?
A chemical formula is a representation of the elements in a molecule. Although the word "formula" connotes an equation, chemical formula are not to be confused with chemical equations, which describe multiple molecules at once.
Definition
A chemical formula is a combination of "chemical symbols," or element symbols such as H, He and Li, used to indicate the number of atoms in a molecule. Chemical formulas are then combined to make "chemical equations" to describe a reaction.
Types
There are two kinds of textual chemical formulas, such as H2O, and several types of graphical formulas that elucidate atom position within the molecule.
Molecular Formula
The molecular chemical formula uses subscripts to count the number of elements in a molecule, e.g. H2O, where the 2 is a subscript. One variant is to clump element symbols together in the order they appear in the molecule, e.g. CH3-O-CH3 or CH3OCH3, instead of C2H6O.
Structural Formula
Structural chemical formulas represent molecules pictorially. They convey angles and positions that a molecular formula couldn't, such as a benzene ring.
Lewis Dot Structure
The most common elements allow up to either 2 or 8 electrons in their outer shell, the shell involved in chemical interactions. The Lewis dot representation of outer-shell electrons exploits the numbers being so low, to show why and how atoms bond with each other with simple diagrams.
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