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In chemistry, the empirical formula of a chemical compound is the simplest whole number ratio of atoms present in a compound. [1] A simple example of this concept is that the empirical formula of sulfur monoxide , or SO, is simply SO, as is the empirical formula of disulfur dioxide , S 2 O 2 .
In most cases the formula representing a formula unit will also be an empirical formula, such as calcium carbonate (CaCO 3) or sodium chloride (NaCl), but it is not always the case. For example, the ionic compounds potassium persulfate ( K 2 S 2 O 8 ), mercury(I) nitrate Hg 2 (NO 3 ) 2 , and sodium peroxide Na 2 O 2 , have empirical formulas of ...
For most ionic compounds dissolved in water, the van 't Hoff factor is equal to the number of discrete ions in a formula unit of the substance. This is true for ideal solutions only, as occasionally ion pairing occurs in solution. At a given instant a small percentage of the ions are paired and count as a single particle.
The Born–Landé equation is a means of calculating the lattice energy of a crystalline ionic compound.In 1918 [1] Max Born and Alfred Landé proposed that the lattice energy could be derived from the electrostatic potential of the ionic lattice and a repulsive potential energy term.
In chemistry, a salt or ionic compound is a chemical compound consisting of an assembly of positively charged ions and negatively charged ions , [1] which results in a compound with no net electric charge (electrically neutral). The constituent ions are held together by electrostatic forces termed ionic bonds.
The molar ionic strength, I, of a solution is a function of the concentration of all ions present in that solution. [3]= = where one half is because we are including both cations and anions, c i is the molar concentration of ion i (M, mol/L), z i is the charge number of that ion, and the sum is taken over all ions in the solution.
For ionic compounds made of molecular cations and/or anions, there may also be ion-dipole and dipole-dipole interactions if either molecule has a molecular dipole moment. The theoretical treatments described below are focused on compounds made of atomic cations and anions, and neglect contributions to the internal energy of the lattice from ...
An effective atomic number in this context is equivalent to the atomic number but is used for compounds (e.g. water) and mixtures of different materials (such as tissue and bone). This is of most interest in terms of radiation interaction with composite materials.