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Any of a subgroup of rare-earth elements, of which the cerium and terbium metals comprise the other two subgroups.

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Conformations

Structures of a compound that differ by the extent of rotation about a single bond.

Square Planar

A term used to describe molecules and polyatomic ions that have one atom in the center and four atoms at the corners of a square.

Molecule

The smallest particle of an element or compound capable of a stable, independent existence.

Hund's Rule

All orbitals of a given sublevel must be occupied by single electrons before pairing begins.

Neutron

A neutral subatomic particle having a mass of 1.0087 amu.

Paramagnetism

Attraction toward a magnetic field, stronger than diamagnetism, but still weak compared to ferromagnetism.

Ionic Compounds

Compounds containing predominantly ionic bonding.

Gel

Colloidal suspension of a solid dispersed in a liquid, a semirigid solid.

Photochemical Smog

A brownish smog occurring in urban areas receiving large amounts of sunlight, caused by photochemical (light-induced) reactions among nitrogen oxides, hydrocarbons and other components of polluted air that produce photochemical oxidants.

 

Heat of Vaporization

The amount of heat required to vaporize one gram of a liquid at its boiling point with no change in temperature. Usually expressed in J/g. The molar heat of vaporization is the amount of heat required to vaporize one mole of liquid at its boiling point with no change in temperature and usually expressed ion kJ/mol.