Atoms

All substances are comprised of extremely large number of particles of matter. The smallest particle which can remain stable (i.e. controlled) and not subdivide into smaller particles is called an ATOM.

All atoms are arrangements of orbiting particles, called ELECTRONS (defined as a negative charge), which swirl around a central group of particles, called the NUCLEUS, (deferred as positive charge), such that the assembly is not unlike that of the astronomer’s explanation of the universal.

In much the same way that space is empty between astronomically - explained bodies, this is also the case when gases are described.

When atoms are combined in-groups by the chemistry of any process which bonds them together such groups are called MOLECULES.

A subscript number deports the number of atoms of an elemental substance in a molecule to the symbol, which denotes the element. Some molecules will only exist in particular arrangements - decided by the chemistry of their internal bonds - and are therefore called MONATOMIC, DIATOMOTIC, TRIATOMIC or POLYATOMIC (for more than 3 atoms).

Hence H2 is hydrogen and is a DIATOMIC MOLECULE (i.e. 2 ATOMS)
CO is CARBOM MONOXIDE and is DIATOMIC
CO2 is CARBON DIOXIDE and is TRIATOMIC
H2O is Steam, Water or ICE and is TRIATOMIC
C8H18 is OCTANE - a hydrocarbon derived from crude petroleum - and is POLYATOMIC.

Note: The carbon monoxide and hydrocarbons, in vehicle exhaust emissions, together with the nitrous oxides NO2, comprise the pollutants which affect the environment.