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A series of reactions (and accompanying enthalpy changes) which, when summed, represents the hypothetical one-step reaction by which elements in their standard states are converted into crystals of ionic compounds (and the accompanying enthalpy changes.)

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Atom

The smallest particle of an element.

ytterbia

Ytterbia is a colorless compound, Yb2O3, used in certain alloys and ceramics. Also known as ytterbium oxide.

Absolute Zero

The zero point on the absolute temperature scale, -273.15°C or 0 K, theoretically, the temperature at which molecular motion ceases. The concept of an absolute zero temperature was first deduced from experiments with gases. When a fixed volume of gas is cooled, its pressure decreases with its temperature. Absolute zero physically possesses quantum mechanical zero-point energy.

Avogadro's Number

The number (6.022x10^23) of atoms, molecules or particles found in exactly 1 mole of substance.

Shielding Effect

Electrons in filled sets of s , p orbitals between the nucleus and outer shell electrons shield the outer shell electrons somewhat from the effect of protons in the nucleus, also called screening effect.

Physical Change

A change in which a substance changes from one physical state to another but no substances with different composition are formed. Example Gas to Liquid - Solid.

 

Electrodes

Surfaces upon which oxidation and reduction half-reactions, occur in electrochemical cells.

Adsorption

Adhesion of a species onto the surfaces of particles.

Open Sextet

Refers to species that have only six electrons in the highest energy level of the central element (many Lewis acids).

Dermal toxicity

Adverse health effects resulting from skin exposure ot a substance.

Basic Salt

A salt containing an ionizable OH group.

Heat Capacity

The amount of heat required to raise the temperature of a body (of any mass) one degree Celsius.

Endothermic

Describes processes that absorb heat energy.

Plasma

A physical state of matter which exists at extremely high temperatures in which all molecules are dissociated and most atoms are ionized.

Acetic Acid

CA3COOH, clear, colorless liquid, pungent odor. Boiling point 140C, flash point 54C (closed cup), autoignition temperature 38OC.

Avogadro's Law

At the same temperature and pressure, equal volumes of all gases contain the same number of molecules.

Matter

Anything that has mass and occupies space.

Saturated Solution

Solution in which no more solute will dissolve.

Polymer

A large molecule consisting of chains or rings of linked monomer units, usually characterized by high melting and boiling points.

Molecular Geometry

The arrangement of atoms (not lone pairs of electrons) around a central atom of a molecule or polyatomic ion.