Subscript Numbers

The elemental makeup of a compound defines its chemical identity, and chemical formulas are the most concise way of representing this elemental makeup. When a compound’s formula is unknown, measuring the mass of its constituent elements is often the first step in determining the formula experimentally. Determination of Empirical Formulas The most common approach to determining a compound’s chemical formula is first to measure the masses of its constituent elements. However, chemical formulas...

Chemical equations represent how a chemical reaction proceeds from reactants to products through physical or chemical change using chemical formulas. Stoichiometry is a term that describes the relative quantities of reactants and products in a chemical reaction. It is based on the Law of Conservation of Mass, which is a fundamental law that states that matter is neither created nor destroyed. Quite simply, the number and identity of reactant atoms must equal the number and identity of product...

A chemical symbol is an abbreviation used to indicate an element or an atom of an element. For example, the symbol for mercury is Hg. The same symbol is used to indicate one atom of mercury (microscopic domain) or to label a container of many atoms of the element mercury (macroscopic domain). Some symbols are derived from the common English name of the element; others are abbreviations of the name in another language — Latin, Greek or German. For example, the symbol for aluminum (common name)...

Homogeneous Equilibria for Gaseous Reactions For gas-phase reactions, the equilibrium constant may be expressed in terms of either the molar concentrations (Kc) or partial pressures (Kp) of the reactants and products. A relation between these two K values may be simply derived from the ideal gas equation and the definition of molarity. According to the ideal gas equation: Molar concentration or molarity is given by number of moles divided by the volume: Thus, where P is partial pressure, V...

Molecular compounds or covalent compounds result when atoms share electrons to form covalent bonds. Since there is no electron transfer, molecular compounds do not contain ions; instead, they consist of discrete, neutral molecules. Since covalent compounds are formed from the combination of nonmetals, the periodic table can help recognize many of them. The position of a compound’s elements in the periodic table can predict whether the compound is ionic or covalent (although there are...