Formula unit 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. Examples include ionic NaCl and KO and covalent networks such as SiO and C (as diamond or graphite). 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
Substance-related disorder Substance-related disorder Substance abuse, also known as drug abuse, is a patterned use of a substance (drug) in which the user consumes the substance in amounts or with methods which are harmful to themselves or others. The drugs used are often associated with levels of intoxication that alter judgment, perception, attention and physical control, not related with medical effects. It is often thought that the main abused substances are illegal drugs and alcohol; however it is becoming more common that prescription drugs and tobacco are a prevalent problem. Substance-related disorders, including both substance dependence and substance abuse, can lead to