Glossary of Terms

Neutrons
Neutrons are electrically neutral fundamental particles of matter. They are found in all atomic nuclei except for the hydrogen atom. The nucleus of the hydrogen atom does not have any neutrons.
The mass of a neutron is approximately 1 amu .
Noble gases
All the elements in Group VIIIA of the periodic table.
Nonmetals
Nonmetals can be found in nature in the uncombined elemental form. They are also found combined with metals, and other nonmetals to form compounds. The nonmetals are:
- H, He, C, N, O, F, Ne, P, S, Cl, Ar, Se, Br, Kr,I, Xe, At, Rn
These are the group of elements that are to the right of the diagonal line on the periodic table.
Nonpolar covalent bond
A type of covalent bond formed by equal sharing of electrons between two identical nonmetals whose electronegativities are the identical.
Octet Rule
This is a rule stating that bonded atoms tend to possess or share a total of eight valence electrons.
Osteoporosis
Osteoporosis is a degenerative bone disease most often found in elderly women. It is linked to a lack of calcium in the diet. It can be corrected, or stopped, if detected early.
Oxidation
A process in which electrons are "lost" and the oxidation state of some atom increases. Oxidation can occur only in combination with reduction.
The corrosion of iron in air is an example of oxidation of iron. This reaction, accelerated by the presence of moisture, forms iron(III) oxide or "rust". This compound is identical with the ore from which the iron was obtained. Thus, corrosion involves a return of the metal to its original state.
Sometimes oxidation may be beneficial to metals. Aluminum is immuned from corrosion because a film of aluminum oxide forms on its surface inhibits degradation.
Oxidation half-reaction
The balanced half-reaction that is written to show the loss of electrons that occurs during oxidation.
- An example of an oxidation half-reaction is
  
  Zn (s) -> Zn⁺²(aq) + 2 e^-
In the oxidation half-reaction, the electron(s) appears on the right-hand-side of the reaction. The oxidation state of zinc increases from zero to +2 corresponding to a loss of two electrons by each zinc atom. Zinc is oxidized.
Oxidation Number
Oxidation number (also oxidation state) is a number that is assigned to each kind of atom in a compound, an ion, or an element by using a set of rules.
Oxidizing agent
The reactant that accepts electron(s) and becomes reduced when another substance is oxidized.
Panning for gold
Gold can be recovered by swirling gold-bearing sand and gravel with water in a pan. The lighter particles spill over the edge and the dense nuggets of gold remain.
Period of elements
A period is a horizontal row in the periodic table.
Periodic law
When elements are arranged in order of increasing atomic number, there is a periodic variation in the physical and chemical properties of elements.
pH
The measure of acidity or H⁺ ions concentration of a solution. pH = - log [H⁺]
Phosphor
A substance which emits radiation in the ultraviolet, visible, or infrared wavelengths during or following excitation by an external energy source. Luminescence of the substance may either be fluorescent or phosphorescent depending on whether or not it emits light after the exciting source is removed.
Phosphors such as metallic tungstates, zinc sulfide, calcium phosphate, are produced in quantity for use in fluorescent lights, colour television, and scintillation counters. The production of these phosphors involves the use of activators such as silver, copper or manganese which are present in trace quantities.
Phosphorescence
A kind of luminescence occurring naturally in many minerals and metallic compounds, in some types of organic compounds, and in some living organisms such as marine fauna and insects such as firefly.
Phosphorescence is distinguished from fluorescence in two ways:
1. There is a longer time period between excitation and the emission of light, ranging from one-thousandth of a second to several hours, whereas fluorescence occurs almost instantaneously, and
2. Phosphorescence may continue for some hours after the exciting source has been removed. The length of emanation depends on the substance, whereas fluorescence ceases when the source is cut off. Thus, phosphorescent materials glow in darkness, but fluorescent materials do not.
Physical change
A change that does not involve changing any substances into any other substances is called a physical change. Some physical changes are: boiling water, grinding sugar into a fine powder, melting wax.
Physical property
This is a characteristic that a substance can display without undergoing a change in its identity.
Physical states
All matter exists in three physical states: solid, liquid, or gas. Although their physical appearances of these three states are different, their chemical makeup in all three states are the same.
Platinum metals
The group of transition metals found in Group VIII of the Periodic Table. They are:
1. ruthenium,
2. osmium,
3. rhodium,
4. iridium,
5. palladium, and
6. platinum.
Their chemical and physical properties are similar, and they occur together in mineral deposits.
Polar bond
See polar covalent bond.
Polar covalent bond
Also known as polar bond. It is a type of covalent bond formed by the unequal sharing of electrons between atoms whose electronegativities differ.
Polyvinyl chloride, PVC
Polyvinyl chloride is produced on a large scale in the USA and in Canada by several companies including Dow Chemical Co. It is a hard non-transparent material which is made useful by the incorporation of plasticizers. The product can be coloured by "filling" with suitable substances. It is used extensively to make household items such as:
- garden hoses, pipe lines, kitchen utensils, toys, raincoats, electrical insulation for cables and swimming pool liners. It is chemically inert and does not corrode or rot. But it decomposes in summer sunlight due to the action of ultraviolet light.
Portland cement
Named for Portland, England, this type of cement is formed when clay and limestone are strongly heated together. This type of cement is a mixture of calcium silicates and aluminosilicates. When mixed with water these substances react to form a gelatinous mass which sets hard when 3-D cross links are formed.
Potash
A generic and commercial name for naturally occurring potassium salts. Its name is derived from pot ashes denoting the ancient method of leaching wood ashes for their potassium carbonate content and concentrating the extract in iron pots.
Potential energy
This is stored energy that an object has by virtue of its position. Chemicals also possess potential energy. This energy is stored in chemicals that can be liberated during chemical reactions. There are different forms of potential energy. For example:
- potential energy due to gravity,
- potential energy stored in a spring,
- potential energy due to chemical bonding.
Principal energy level
Electrons in an atom occupy specific energy levels that increase in energy as they increase in distance from the nucleus. These energy levels, designated by n where n=1,2,3,...7, are called principal energy levels.
Protons
Protons are positively charged fundamental particles. They are found in the nuclei of all atoms. The number of protons determines the identity of an element. The mass of a proton is approximately 1 amu .
Pyrex
The major components of glass are fused sodium silicate, Na₂SiO₃, and calcium silicate, CaSiO₃. Pyrex is a type of borosilicate glass that uses boron to replace some of the sodium and calcium and has a higher percentage of silica. As a result, pyrex is more resistant to chemical attack and is able to withstand greater thermal and mechanical stress.
Rare-earths
The elements of atomic number 57 through 71 are known as the Lanthanide elements. The lanthanide elements, scandium (atomic number=21), and yttrium (atomic number=39) are known as the rare-earth elements.
This name for the group is no longer appropriate because most of them are available in far greater quantities than originally thought. In fact the absolute abundances in the lithosphere are relatively high. However, traditions prevail!
The rare-earth elements are all metals. They are all sufficiently reactive that none exists in nature as the elemental metal.
Reducing agent
The reactant that donates the electron(s) and becomes oxidized when another substance is reduced.
Reduction
A process in which electrons are "gained" and the oxidation state of some atom decreases. Reduction can only occur in combination with oxidation.
Reduction half-reaction
The balanced half-reaction that is written to show the gain of electrons that occurs during reduction.
- An example of a reduction half-reaction is
  
  Cu⁺²(aq) + 2 e^- -> Cu(s)
In the reduction half-reaction, the electron(s) appears on the left-hand-side of the reaction. The oxidation state of copper decreases from +2 to zero corresponding to the gain of two electrons by each Cu²⁺ ion. Cu⁺² is reduced.
Refluxing
The process of boiling a liquid in a vessel connected to a condenser, so that the liquid runs back into the vessel. By using a reflux condenser, the liquid can be maintained at its boiling point for long periods of time, without evaporation. The technique is a standard method of carrying out reactions in organic chemistry.
Representative Elements
All the 'A' group elements in the periodic table.

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All contents copyrighted © 1997 - 2004
 Chemistry Department
British Columbia Institute of Technology, Burnaby, B.C. Canada.
All Rights reserved

Neutrons

Noble gases

Nonmetals

Nonpolar covalent bond

Octet Rule

Osteoporosis

Oxidation

Oxidation half-reaction

Oxidation Number

Oxidizing agent

Panning for gold

Period of elements

Periodic law

pH

Phosphor

Phosphorescence

Physical change

Physical property

Physical states

Platinum metals

Polar bond

Polar covalent bond

Polyvinyl chloride, PVC

Portland cement

Potash

Potential energy

Principal energy level

Protons

Pyrex

Rare-earths

Reducing agent

Reduction

Reduction half-reaction

Refluxing

Representative Elements