Formula unit

A formula unit in chemistry is the empirical formula of any ionic or covalent network solid compound used as an independent entity for stoichiometric calculations. It is the lowest whole number ratio of ions represented in an ionic compound.^[1] Examples include ionic NaCl and K₂O and covalent networks such as SiO₂ and C (as diamond or graphite).^[2]

Ionic compounds do not exist as individual molecules; a formula unit thus indicates the lowest reduced ratio of ions in the compound.

A chemical formula shows the kinds and numbers of atoms in the smallest representative unit of a substance.

In mineralogy, as minerals are almost exclusively either ionic or network solids, the formula unit is used. The number of formula units (Z) and the dimensions of the crystallographic axes are used in defining the unit cell.^[3]

References

↑ Molecular Formula on science.jrank.org
↑ Steven S. Zumdahl; Susan A. Zumdahl (2000), Chemistry (5 ed.), Houghton Mifflin, pp. 470-6, ISBN 0-618-03591-5
↑ Smyth, Joseph R. and Tamsin C. McCormick, 1995, Crystallographic Data for Minerals, American Geophysical Union

Mole concepts

Physical quantities	Mass concentration Molar concentration Molality Mass Volume Density Mole fraction Mass fraction Amount of substance Molar mass Atomic mass Particle number Avogadro constant Pressure Kelvin temperature Gas constant Molar volume Specific volume

Laws	Charles's law Boyle's law Gay-Lussac's law Combined gas law Ideal gas law

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