Macroscopic Properties

Properties that can be measured directly.

Magnetic Quantum Number

The spatial orientation of the orbital.

Manometer

A device used to measure the pressure of a gas in a laboratory experiment.

Many-Electron Atoms

Atoms that contain two or more electrons.

Mass

A measure of the quantity of matter contained in an object.

Mass Defect

The difference between the mass of an atom and the sum of the masses of its protons, neutrons, and electrons.

Mass Number

(A) - The total number of neutrons and protons present in the nucleus of an atom.

Matter

Anything that occupies space and possesses mass.

Mean Square Speed

The average of the square of the speeds of all the molecules.

Melting Point

The temperature at which solid and liquid phases coexist in equilibrium.

Mesosphere

The uppermost layer of the atmosphere.

Metalloid

An element with properties intermediate between those of metals and nonmetals.

Metallurgy

The science and technology of separating metals from their ores and of compounding alloys.

Metals

Elements that are good conductors of heat and electricity and have the tendency to form positive ions in ionic compounds.

Metathesis

Another name for a double displacement reaction. See displacement reaction.

Microscopic Properties

Properties that cannot be measured directly without the aid of a microscope or other special instrument.

Mineral

A naturally occurring substance with a range of chemical composition.

Miscible

Two liquids that are completely soluble in each other in all proportions are said to be miscible.

Mixture

A combination of two or more substances in which the substances retain their identity.

Moderator

A substance that can reduce the kinetic energy of neutrons.

Molality

The number of moles of solute dissolved in one kilogram of solvent.

Molar Concentration

See molarity.

Molar Heat Capacity

The quantity of heat required to change the temperature of 1 mol of a substance by 1 K.

Molar Heat of Fusion

The energy (in kilojoules) required to melt one mole of a solid.

Molar Heat of Sublimation

The energy (in kilojoules) required to sublime one mole of a solid.

Molar Heat of Vaporization

The energy (in kilojoules) required to vaporize one mole of a liquid.

Molar Mass

The mass (in grams or kilograms) of one mole of atoms, molecules, or other particles.

Molar Solubility

The number of moles of solute in one liter of a saturated solution (mol/L).

Molarity

The number of moles of solute in one liter of solution.

Mole

The amount of substance that contains as many elementary entities (atoms, molecules, or other particles) as there are atoms in exactly 12 grams (or 0.012 kilograms) of the carbon-12 isotope.

Mole Fraction

Ratio of the number of moles of one component of a mixture to the total number of moles of all components in the mixture.

Mole Method

An approach for determining the amount of product formed in a reaction.

Molecular Equations

Equations in which the formulas of the compounds are written as though all species existed as molecules or whole units.

Molecular Formula

An expression showing the exact numbers of atoms of each element in a molecule.

Molecular Mass

The sum of the atomic masses (in amu) present in the molecule.

Molecular Orbital

An orbital that results from the interaction of the atomic orbitals of the bonding atoms.

Molecularity of a Reaction

The number of molecules reacting in an elementary step.

Molecule

An aggregate of at least two atoms in a definite arrangement held together by special forces.

Monatomic Ion

An ion that contains only one atom.

Monomer

The single repeating unit of a polymer.

Monoprotic Acid

Each unit of the acid yields one hydrogen ion upon ionization.

Monosaccharide

A simple sugar; a polyhydroxy ketone or aldehyde of three to nine C atoms.

Multiple Bonds

Bonds formed when two atoms share two or more pairs of electrons.