Chemical formula

A chemical formula is an easy way of expressing information about the atoms that constitute a particular chemical compound, and how the relationship between those atoms changes in chemical reactions. History See also Atomic theory, Atomism The concept that matter is composed of discrete units and cannot be divided into arbitrarily tiny A chemical compound is a substance consisting of two or more different elements chemically bonded together in a fixed proportion by Mass. A chemical reaction is a process that always results in the interconversion of Chemical substances The substance or substances initially involved in a chemical reaction are called For molecular compounds it is also known as the molecular formula, and identifies each constituent element by its chemical symbol and indicates the number of atoms of each element found in each discrete molecule of that compound. In Chemistry, a molecule is defined as a sufficiently stable electrically neutral group of at least two Atoms in a definite arrangement held together by A chemical element is a type of Atom that is distinguished by its Atomic number; that is by the number of Protons in its nucleus. See also Chemical formula. A chemical symbol is an Abbreviation or shortened version of the name of a Chemical element In Chemistry, a molecule is defined as a sufficiently stable electrically neutral group of at least two Atoms in a definite arrangement held together by If a molecule contains more than one atom of a particular element, this quantity is indicated using a subscript after the chemical symbol (although 19th-century books often used superscripts). This article is about the terms 'subscript' and 'superscript' as used in typography For ionic compounds and other non-molecular substances, the subscripts indicate the ratio of elements in the empirical formula. In Chemistry, an ionic compound is a Chemical compound in which Ions are held together in a lattice structure by Ionic bonds Usually the positively Use in chemistry In Chemistry, the empirical formula of a Chemical compound is a simple expression of the relative number of each type of Atom

This system for writing chemical formulas was invented by the 19th-century Swedish chemist Jons Jakob Berzelius. Friherre Jöns Jacob Berzelius (20 August 1779 &ndash 7 August 1848 was a Swedish chemist

1 Molecular and structural formula
2 Polymers
3 Ions
4 Isotopes
5 Empirical formula
6 Trapped atoms
7 Non-stoichiometric formulas
8 General forms for organic compounds
9 Hill System
10 References
11 See also

Molecular and structural formula

For example methane, a simple molecule consisting of one carbon atom bonded to four hydrogen atoms, has the chemical formula:

CH₄

and glucose with six carbon atoms, twelve hydrogen atoms and six oxygen atoms has the chemical formula:

C₆H₁₂O₆. Methane is a Chemical compound with the molecular formula. It is the simplest Alkane, and the principal component of Natural gas. Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 Glucose (Glc a Monosaccharide (or simple Sugar) also known as grape sugar, is an important Carbohydrate in Biology. Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the

A chemical formula supplies information about the types and spatial arrangement of bonds in the chemical, though it does not necessarily specify the exact isomer. A chemical bond is the physical process responsible for the attractive interactions between Atoms and Molecules and which confers stability to diatomic and polyatomic This article is about the chemical concept For "isomerism" of atomic nuclei see Nuclear isomer. For example ethane consists of two carbon atoms single-bonded to each other, with each carbon atom having three hydrogen atoms bonded to it. ETHANE is a mnemonic indicating a protocol used by Emergency services to report situations which they may be faced with especially as it relates to major incidents where Its chemical formula can be rendered as CH₃CH₃. In ethylene there is a double bond between the carbon atoms (and thus each carbon only has two hydrogens), therefore the chemical formula may be written: CH₂CH₂, and the fact that there is a double bond between the carbons is implicit because carbon has a valence of four. Structure This Hydrocarbon has four Hydrogen Atoms bound to a pair of Carbon atoms that are connected by a Double bond. However, a more explicit and correct method is to write H₂C=CH₂ or less commonly H₂C::CH₂. The two lines (or two pairs of dots) indicate that a double bond connects the atoms on either side of them.

A triple bond may be expressed with three lines or pairs of dots, and if there may be ambiguity, a single line or pair of dots may be used to indicate a single bond.

Molecules with multiple functional groups that are the same may be expressed in the following way: (CH₃)₃CH. In Organic chemistry, functional groups are specific groups of Atoms within Molecules that are responsible for the characteristic Chemical reactions However, this implies a different structure from other molecules that can be formed using the same atoms (isomers). The formula (CH₃)₃CH implies a chain of three carbon atoms, with the middle carbon atom bonded to another carbon (see image of 4 carbon "C" atoms),

and the remaining bonds on the carbons all leading to hydrogen atoms (hydrogen atoms are not shown in image). However, the same number of atoms (10 hydrogens and 4 carbons, or C₄H₁₀) may be used to make a straight chain: CH₃CH₂CH₂CH₃.

The alkene but-2-ene has two isomers which the chemical formula CH₃CH=CHCH₃ does not identify. The relative position of the two methyl groups must be indicated by additional notation denoting whether the methyl groups are on the same side of the double bond (cis or Z) or on the opposite sides from each other (trans or E).

Polymers

For polymers, parentheses are placed around the repeating unit. A polymer is a large Molecule ( Macromolecule) composed of repeating Structural units typically connected by Covalent Chemical bonds For example, a hydrocarbon molecule that is described as: CH₃(CH₂)₅₀CH₃, is a molecule with 50 repeating units. In Organic chemistry, a hydrocarbon is an Organic compound consisting entirely of Hydrogen and Carbon. If the number of repeating units is unknown or variable, the letter n may be used to indicate this: CH₃(CH₂)_nCH₃.

Ions

For ions, the charge on a particular atom may be denoted with a right-hand superscript. An ion is an Atom or Molecule which has lost or gained one or more Valence electrons giving it a positive or negative electrical charge For example Na⁺, or Cu²⁺. The total charge on a charged molecule or a polyatomic ion may also be shown in this way. A polyatomic ion is a charged species ( Ion) composed of two or more atoms covalently bonded or of a metal complex that can be considered as acting For example: hydronium, H₃O⁺ or sulfate, SO₄^2-.

For more complex ions, brackets [ ] are often used to enclose the ionic formula, as in [B₁₂H₁₂]^2-. Parentheses ( ) can be nested inside brackets to indicate a repeating unit, as in [Co(NH₃)₆]³⁺. Here (NH₃)₆ indicates that the ion contains six NH₃ groups, and [ ] encloses the entire formula of the ion with charge +3.

Isotopes

Although isotopes are more relevant to nuclear chemistry or stable isotope chemistry than to conventional chemistry, different isotopes may be indicated with a left-hand superscript in a chemical formula. Isotopes (Greek isos = "equal" tópos = "site place" are any of the different types of atoms ( Nuclides Nuclear chemistry is a subfield of Chemistry dealing with Radioactivity, nuclear processes and nuclear properties Stable isotopes are chemical isotopes that are not Radioactive (to current knowledge This article is about the terms 'subscript' and 'superscript' as used in typography For example, the phosphate ion containing radioactive phosphorus-32 is ³²PO₄^3-. Also a study involving stable isotope ratios might include the molecule ¹⁸O¹⁶O.

A left-hand subscript is sometimes used to indicate redundantly the atomic number. See also List of elements by atomic number In Chemistry and Physics, the atomic number (also known as the proton For example, ₈O₂ for dioxygen, and ¹⁶₈O₂ for the most abundant isotopic species of dioxygen. This is convenient when writing equations for nuclear reactions, in order to show the balance of charge more clearly. In Nuclear physics, a nuclear reaction is the process in which two nuclei or nuclear particles collide to produce products different from the initial particles

Empirical formula

In chemistry, the empirical formula of a chemical is a simple expression of the relative number of each type of atom or ratio of the elements in the compound. Chemistry (from Egyptian kēme (chem meaning "earth") is the Science concerned with the composition structure and properties Use in chemistry In Chemistry, the empirical formula of a Chemical compound is a simple expression of the relative number of each type of Atom Empirical formulas are the standard for ionic compounds, such as CaCl₂, and for macromolecules, such as SiO₂. An empirical formula makes no reference to isomerism, structure, or absolute number of atoms. This article is about the chemical concept For "isomerism" of atomic nuclei see Nuclear isomer. The term empirical refers to the process of elemental analysis, a technique of analytical chemistry used to determine the relative percent composition of a pure chemical substance by element. Elemental analysis is a process where a sample of some material (e Analytical chemistry is the study of the Chemical composition of natural and artificial Materials.

For example hexane has a molecular formula of C₆H₁₄, or structurally CH₃CH₂CH₂CH₂CH₂CH₃, implying that it has a chain structure of 6 carbon atoms, and 14 hydrogen atoms. Hexane is an Alkane Hydrocarbon with the Chemical formula CH3(CH24CH3 or C6H14 Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 However, the empirical formula for hexane is C₃H₇. Likewise the empirical formula for hydrogen peroxide, H₂O₂, is simply HO expressing the 1:1 ratio of component elements. Hydrogen peroxide (H2O2 is a very pale blue liquid which appears colorless in a dilute solution slightly more Viscous than water

Trapped atoms

The @ symbol ("at") indicates an atom or molecule trapped inside a cage but not chemically bound to it. This notation became popular in the 1990s with the discovery of fullerene cages, which can trap atoms such as La to form La@C₆₀ or La@C₈₂ for example. "C60" and "C-60" redirect here For other uses see C60 (disambiguation. A non-fullerene example is [As@Ni₁₂As₂₀]^3-, an ion in which one As atom is trapped in a cage formed by the other 32 atoms.

Non-stoichiometric formulas

Main article: Non-stoichiometric compound

Chemical formulas most often use integers for each element. Non-stoichiometric compounds are Chemical compounds with an elemental composition that cannot be represented by a ratio of well-defined Natural numbers and The integers (from the Latin integer, literally "untouched" hence "whole" the word entire comes from the same origin but via French However, there is a whole class of compounds, called non-stoichiometric compounds, that cannot be represented by small integers. Non-stoichiometric compounds are Chemical compounds with an elemental composition that cannot be represented by a ratio of well-defined Natural numbers and Such a formula might be written using decimal fractions, as in Fe_{0. The decimal ( base ten or occasionally denary) Numeral system has ten as its base. 95}O, or it might include a variable part represented by a letter, as in Fe_1–xO, where x is normally much less than 1.

General forms for organic compounds

Chemical formula used for a series of compounds that differ from each other by a constant unit is called general formula. Such a series is called the homologous series, while its members are called homologs. In Chemistry, a homologous series is a series of Organic compounds with a similar General formula, possessing similar chemical properties due to the presence The Hill system is a common convention for writing and sorting formulas. The Hill system is a system of writing Chemical formulas such that the number of Carbon Atoms in a Molecule is indicated first the number of

Hill System

Main article: Hill system

The Hill system is a system of writing chemical formulas such that the number of carbon atoms in a molecule is indicated first, the number of hydrogen atoms next, and then the number of all other chemical elements subsequently, in alphabetical order. The Hill system is a system of writing Chemical formulas such that the number of Carbon Atoms in a Molecule is indicated first the number of Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 History See also Atomic theory, Atomism The concept that matter is composed of discrete units and cannot be divided into arbitrarily tiny In Chemistry, a molecule is defined as a sufficiently stable electrically neutral group of at least two Atoms in a definite arrangement held together by Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 A chemical element is a type of Atom that is distinguished by its Atomic number; that is by the number of Protons in its nucleus. When the formula contains no carbon, all the elements, including hydrogen, are listed alphabetically.

References

Ralph S. Petrucci, William S. Harwood and F. Geoffrey Herring, General Chemistry, 8th Edition (Prentice-Hall 2002), chapter 3.

Dictionary

-noun

Alternative name for molecular formula.

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