The pressure that must be applied to a solution to prevent the passage of a pure solvent through a
semipermeable membrane across its concentration gradient.
Oxidation
A reaction involving the net loss of electrons or, equivalently, an increase in oxidation number.
Oxidation number
The number assigned to an atom in an ion or molecule that denotes its real or hypothetical charge.
Atoms, alone or in molecules, of standard state elements have oxidation numbers of zero. Also
called the oxidation state.
Oxidizing agent
In a redox reaction, a species that gains electrons and is thereby reduced.
p subshell
The subshells corresponding to the angular momentum quantum number l = 1, found in the second
and higher principal energy levels. Each subshell contains three dumbbell-shaped p orbitals
oriented perpendicular to each other, and referred to as the px, py, and pz orbitals.
Paired electrons
Two electrons in the same orbital with assigned spins of and . See Orbital; Hund’s rule.
Paramagnetism
A property of a substance that contains unpaired electrons, whereby the substance is attracted by a
magnetic field.
Partial pressure
The pressure that one component of a gaseous mixture would exert if it were alone in the container.