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Chemistry - A Molecular World - Molecules

Atoms are rarely found on their own, they usually bond together to form molecules or large lattice structures.

A molecule is a group of atoms that are bonded together to form the smallest piece of a substance that normally exists on its own.

A molecule is defined as a stable, electrically neutral group of two or more atoms in a definite arrangement, held together by very strong covalent bonds.

Molecular chemistry deals with the laws governing the interaction between molecules that results in the formation and breakage of chemical bonds.

Most molecules are far too small to be seen with the naked eye, but there are exceptions; DNA, a macromolecule can reach macroscopic sizes, as can molecules of many polymers.

The first molecules are believed to have been formed in space. Some atoms which came out of a supernova were too light, and so moved too fast, to glue together with ionic bonds.

They travelled out of the star until they were cool enough to attach to a dust grain. There these light atoms met and join together with a new type of bond called a covalent bond.

Molecules are the building blocks of life, made mostly of the atoms hydrogen, oxygen, nitrogen and carbon.

The molecular weight of any molecule is the sum of the atomic weights of all its atoms.

Since the atomic weight of a hydrogen atom is 1.008 amu (relative to carbon-12 as exactly 12 amu), the molecular weight of the H2 molecule is twice this value, or 2.016 amu.


Shells and Bonding

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