or more hydrocarbon radicals for hydrogen atoms.amino acid One of the “building blocks” of proteins; contains one or more NH 2 −
groups that have replaced the same number of hydrogen atoms in an organic
acid.amorphous Having no definite crystalline structure.
amphoteric Referring to a hydroxide that may have either acidic or basic
properties, depending on the substance with which it reacts.
analysis The breaking down of a compound into two or more simpler substances.
anhydride A compound derived from another compound by the removal of water;
it will combine with water to form an acid (acidic anhydride) or a base (basic
anhydride).
anhydrous Containing no water.
anion An ion or particle that has a negative charge and thus is attracted to a
positively charged anode.
anode The electrode in an electrolytic cell that has a positive charge and attracts
negative ions.
antichlor A substance used to remove the excess of chlorine in the bleaching
process.
aromatic compound A compound whose basic structure contains the benzene
ring; it usually has an odor.
atmosphere The layer of gases surrounding Earth; also, a unit of pressure (1 atm
= approx. 760 mm of Hg or torr).
atom The smallest particle of an element that retains the properties of that
element and can enter into a chemical reaction.
atomic energy See nuclear energy, a more accurate term.
atomic mass (relative atomic mass or atomic weight) The average mean value
of the isotopic masses of the atoms of an element. It indicates the relative mass
of the element as compared with that of carbon-12, which is assigned a mass of
exactly 12 atomic mass units.
atomic mass unit One twelfth of the mass of a carbon-12 atom; equivalent to
1.660531 × 10−27 kilogram (abbreviation: amu or μ).atomic number The number that indicates the order of an element in the periodic
system; numerically equal to the number of protons in the nucleus of the atom,
or the number of negative electrons located outside the nucleus of the atom.
atomic radius One-half the distance between adjacent nuclei in the crystalline or
solid phase of an element; the distance from the atomic nucleus to the valence
electrons.
atomic weight See atomic mass.
Aufbau Principle The principle that states that an electron occupies the lowest
energy orbital that can receive it.