A chemical composition specifies the identity, arrangement, and ratio of the

chemical element A chemical element is a chemical substance whose atoms all have the same number of protons. The number of protons is called the atomic number of that element. For example, oxygen has an atomic number of 8: each oxygen atom has 8 protons in its ...

s making up a compound by way of chemical and atomic bonds. Chemical formulas can be used to describe the relative amounts of elements present in a compound. For example, the chemical formula for

water Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...

is H₂O: this means that each

molecule A molecule is a group of two or more atoms that are held together by Force, attractive forces known as chemical bonds; depending on context, the term may or may not include ions that satisfy this criterion. In quantum physics, organic chemi ...

of water is constituted by 2

atom Atoms are the basic particles of the chemical elements. An atom consists of a atomic nucleus, nucleus of protons and generally neutrons, surrounded by an electromagnetically bound swarm of electrons. The chemical elements are distinguished fr ...

s of

hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...

(H) and 1 atom of

oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...

(O). The chemical composition of water may be interpreted as a 2:1 ratio of hydrogen atoms to oxygen atoms. Different types of chemical formulas are used to convey composition information, such as an

empirical Empirical evidence is evidence obtained through sense experience or experimental procedure. It is of central importance to the sciences and plays a role in various other fields, like epistemology and law. There is no general agreement on how t ...

or molecular formula.

Nomenclature Nomenclature (, ) is a system of names or terms, or the rules for forming these terms in a particular field of arts or sciences. (The theoretical field studying nomenclature is sometimes referred to as ''onymology'' or ''taxonymy'' ). The principl ...

can be used to express not only the elements present in a compound but their arrangement within the

molecules A molecule is a group of two or more atoms that are held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions that satisfy this criterion. In quantum physics, organic chemistry ...

of the compound. In this way, compounds will have unique names which can describe their elemental composition.

Composite mixture

The chemical composition of a

mixture In chemistry, a mixture is a material made up of two or more different chemical substances which can be separated by physical method. It is an impure substance made up of 2 or more elements or compounds mechanically mixed together in any proporti ...

can be defined as the distribution of the individual substances that constitute the mixture, called "components". In other words, it is equivalent to quantifying the

concentration In chemistry, concentration is the abundance of a constituent divided by the total volume of a mixture. Several types of mathematical description can be distinguished: '' mass concentration'', '' molar concentration'', '' number concentration'', ...

of each component. Because there are different ways to define the concentration of a component, there are also different ways to define the composition of a mixture. It may be expressed as

molar fraction In chemistry, the Mole (unit), mole fraction or molar fraction, also called mole proportion or molar proportion, is a quantity (science), quantity defined as the ratio between the amount of substance, amount of a constituent substance, ''ni'' (ex ...

volume fraction In chemistry and fluid mechanics, the volume fraction \varphi_i is defined as the volume of a constituent ''V'i'' divided by the volume of all constituents of the mixture ''V'' prior to mixing: :\varphi_i = \frac . Being dimensionless quantit ...

, mass fraction,

molality In chemistry, molality is a measure of the amount of solute in a solution relative to a given mass of solvent. This contrasts with the definition of '' molarity'' which is based on a given volume of solution. A commonly used unit for molality ...

, molarity or normality or

mixing ratio In chemistry and physics, the dimensionless mixing ratio is the abundance of one component of a mixture relative to that of all other components. The term can refer either to mole ratio (see concentration) or mass ratio (see stoichiometry). In a ...

. Chemical composition of a mixture can be represented graphically in plots like ternary plot and quaternary plot.

References

{{reflist Chemical properties Analytical chemistry