Formula unit
In chemistry, a formula unit is the smallest unit of a non-molecular substance, such as an ionic compound, covalent network solid, or metal.[1] It can also refer to the chemical formula for that unit. Those structures do not consist of discrete molecules, and so for them, the term formula unit is used. In contrast, the terms molecule or molecular formula are applied to molecules.[2] The formula unit is used as an independent entity for stoichiometric calculations.[3] Examples of formula units, include ionic compounds such as Page Module:Chem2/styles.css has no content.NaCl and Page Module:Chem2/styles.css has no content.K2O and covalent networks such as Page Module:Chem2/styles.css has no content.SiO2 and C (as diamond or graphite).[4]
In most cases the formula representing a formula unit will also be an empirical formula, such as calcium carbonate (Page Module:Chem2/styles.css has no content.CaCO3) or sodium chloride (Page Module:Chem2/styles.css has no content.NaCl), but it is not always the case. For example, the ionic compounds potassium persulfate (Page Module:Chem2/styles.css has no content.K2S2O8), mercury(I) nitrate Page Module:Chem2/styles.css has no content.Hg2(NO3)2, and sodium peroxide Page Module:Chem2/styles.css has no content.Na2O2, have empirical formulas of Page Module:Chem2/styles.css has no content.KSO4, Page Module:Chem2/styles.css has no content.HgNO3, and Page Module:Chem2/styles.css has no content.NaO, respectively, being presented in the simplest whole number ratios.[citation needed]
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.[5]
References
Page Template:Reflist/styles.css has no content.
- ^ Peter Atkins, Julio de Paula, Ronald Friedman, Physical Chemistry: Quanta, Matter, and Change, 2nd Edition
- ^ Page Module:Citation/CS1/styles.css has no content."Chapter 4 – Covalent Bonds and Molecular Compounds". wou.edu. Retrieved 2023-10-08.
- ^ Page Module:Citation/CS1/styles.css has no content."2.2: Chemical Formulas". Chemistry LibreTexts. 2015-01-27. Retrieved 2023-09-10.
- ^ Steven S. Zumdahl; Susan A. Zumdahl (2000), Chemistry (5 ed.), Houghton Mifflin, pp. 470-6, Template:ISBN
- ^ Smyth, Joseph R. and Tamsin C. McCormick, 1995, Crystallographic Data for Minerals, American Geophysical Union
Lua error in package.lua at line 80: module 'Module:Navbox/configuration' not found.
