CHEM1006 Lecture Notes - Lecture 20: Isobutane, Chemical Formula, Butane
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Lecture 20
Chemists use a variety of notations to describe and
summarize the atomic constituents of compounds.
These notations, which include empirical, molecular, and
structural formulas, use the chemical symbols for the
elements along with numeric values to describe atomic
composition.
Empirical formulas are the simplest form of notation.
They provide the lowest whole-number ratio between the
elements in a compound.
Unlike molecular formulas, they do not provide
information about the absolute number of atoms in a
single molecule of a compound.
The molecular formula for a compound is equal to, or a
whole-number multiple of, its empirical formula.
An empirical formula lacks any structural information
about the positioning or bonding of atoms in a molecule.
It can therefore describe a number of different
structures, or isomers, with varying physical properties.
For butane and isobutane, the empirical formula for both
molecules is C2H5, and they share the same molecular
formula, C4H10.
One structural representation for butane is
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