Poissons ratio of a material is defined as the ratio of the lateral strain change in the width per unit width of a material to the axial strain change in its length per unit length due to the action of a Force. A formula unit is a term used for defining the whole lesser number of ratios of ions in an ionic compound. For example KCl is a formula unit comprised of and.
Formula unit definition of an ionic compound that does not form molecules as most salts the chemical formula with the least number of elements out of the set of empirical formulas having the same proportion of ions as elements.
Examples include ionic NaCl and K2O and covalent networks such as SiO2 and C as diamond or graphiteIonic compounds do not exist as individual molecules. When we look at any given ionic compound it is made up of molecules out of which one molecule is positively charged and the other one is negatively charged. NaCl is the formula unit for the ionic compound sodium chloride. It is related to the concept of an empirical formula which is the simplest chemical formula expression for a non-ionic chemical compound.