This is a rule stating that bonded atoms tend to possess or share a total of eight
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.
A process in which electrons are "lost" and the oxidation state of
some atom increases. Oxidation can occur only in combination with
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.
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 (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.
The reactant that accepts electron(s) and becomes
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.
When elements are arranged in order of increasing
atomic number, there is a periodic variation in the physical and chemical
properties of elements.
The measure of acidity or H+ ions concentration of
pH = - log [H+]
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
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.
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:
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
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.
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,
This is a characteristic that a substance can
display without undergoing a change in its identity.
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.
The group of transition metals found in Group VIII of the
Periodic Table. They are:
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.
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.
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.
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 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
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
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.
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
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.
The reactant that donates the electron(s) and becomes oxidized
when another substance is reduced.
A process in which electrons are "gained" and the oxidation
state of some atom decreases. Reduction can only occur in combination with
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.
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.