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A pure substance is composed of molecules with the same average geometrical structure. The chemical formula and the structure of a molecule are the two important factors that determine its properties, particularly its reactivity. Isomers share a chemical formula but normally have very different properties because of their different structures.
A molecule is an electrically neutral group of two or more atoms held together by chemical bonds. [ 16 ] [ 17 ] [ 18 ] A molecule may be homonuclear , that is, it consists of atoms of one chemical element, as with two atoms in the oxygen molecule (O 2 ); or it may be heteronuclear , a chemical compound composed of more than one element, as with ...
Molecular dimers are often formed by the reaction of two identical compounds e.g.: 2A → A−A. In this example, monomer "A" is said to dimerize to give the dimer "A−A". Dicyclopentadiene is an asymmetrical dimer of two cyclopentadiene molecules that have reacted in a Diels-Alder reaction to give the product. Upon heating, it "cracks ...
Covalent bonding of two hydrogen atoms to form a hydrogen molecule, H 2. In (a) the two nuclei are surrounded by a cloud of two electrons in the bonding orbital that holds the molecule together. (b) shows hydrogen's antibonding orbital, which is higher in energy and is normally not occupied by any electrons.
A diatomic hydrogen molecule, H 2 (right), is formed by a covalent bond when two single hydrogen atoms share two electrons between them. critical point The end point of a phase equilibrium curve or pressure-temperature curve at which conditions are such that phase boundaries vanish and a substance's different phases, such as liquid and vapor ...
They can be broken into two categories: homonuclear and heteronuclear. A homonuclear diatomic molecule is one composed of two atoms of the same element. Examples are H 2, O 2, and N 2. A heteronuclear diatomic molecule is composed of two atoms of two different elements. Examples include CO, HCl, and NO.
It is considered a "half bond" because it consists of only one shared electron (rather than two); [13] in molecular orbital terms, the third electron is in an anti-bonding orbital which cancels out half of the bond formed by the other two electrons. Another example of a molecule containing a 3-electron bond, in addition to two 2-electron bonds ...
Cyclic rearrangements include cycloadditions and, more generally, pericyclic reactions, wherein two or more double bond-containing molecules form a cyclic molecule. An important example of cycloaddition reaction is the Diels–Alder reaction (the so-called [4+2] cycloaddition) between a conjugated diene and a substituted alkene to form a ...