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.

• Oxidation

  A process in which electrons are "lost" and the oxidation state of some atom increases. Oxidation can occur only in combination with reduction.

• 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 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.

• 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

  pH is a measure of acidity or H⁺ concentration of a solution. Mathematically, pH = - log [H⁺]

  where, [H⁺] is the concentration of H⁺ of the solution in unit of molarity.
  The lower the pH, the more acidic the solution.

• 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.

• pH

  pOH is a measure of basicity or OH^- concentration of a solution. Mathematically, pOH = - log [OH^-]

  where, [OH^-] is the concentration of OH^- of the solution in unit of molarity.
  The lower the pOH, the more basic the solution.

• 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.

• 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 .

• 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.

• Representative Elements

  All the 'A' group elements in the periodic table.

Rosamaría Fong, Instructor of Chemistry,
British Columbia Institute of Technology, Burnaby, B.C. Canada.

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All contents copyrighted © 1996
Rosamaría Fong, Instructor of Chemistry
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: Last updated on August 3, 1996