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960 terms · page 30 of 40
Polar Covalent Bond
Chemical Bonding & Molecular Structure
D
A covalent bond in which the shared electrons are unequally distributed because the bonded atoms differ in electronegativity.
δ⁺A—Bδ⁻
Polarisability
Chemical Bonding & Molecular Structure
C·m²/V
The ease with which the electron cloud of an atom, ion or molecule can be distorted by an external electric field.
μ_induced = α × E
Polarising Power
Chemical Bonding & Molecular Structure
Dimensionless
The ability of a cation to distort the electron cloud of a neighbouring anion.
∝ charge / radius²
Polyatomic Ion
Foundations of Chemistry
C (charge)
A covalently bonded group of atoms that carries an overall electrical charge and behaves as a single unit in reactions.
Polydentate Ligand
Inorganic & Coordination Chemistry
Dimensionless
A ligand that binds to a single metal centre through three or more donor atoms.
Polymer
Biochemistry & Polymer Chemistry
g/mol
A large molecule built from many repeating structural units joined by covalent bonds.
–(A)ₙ–
Polymorphism
States of Matter & Gas Laws
Dimensionless
The ability of a single substance to exist in more than one crystalline form.
Polyprotic Acid
Acids, Bases & Salts
mol/L
An acid capable of donating more than one proton per molecule.
H₂A ⇌ H⁺ + HA⁻ ⇌ 2H⁺ + A²⁻
Polysaccharide
Biochemistry & Polymer Chemistry
Dimensionless
A carbohydrate polymer built from many monosaccharide units linked by glycosidic bonds.
(C₆H₁₀O₅)ₙ
Position Isomerism
Organic Chemistry
Dimensionless
Structural isomerism arising from a functional group occupying different positions on the same carbon skeleton.
Positive Deviation
Solutions & Colligative Properties
Pa
Behaviour in which a solution exerts a higher vapour pressure than Raoult's law predicts.
p > x p°
Positron Emission
Nuclear & Radiochemistry
MeV
Radioactive decay in which a proton converts into a neutron, emitting a positron and a neutrino.
p → n + e⁺ + ν
Pre-exponential Factor
Chemical Kinetics & Catalysis
Various
The constant A in the Arrhenius equation, representing the frequency of appropriately oriented collisions.
A = pZ
Precipitate
Stoichiometry & Chemical Reactions
g
An insoluble solid that separates from a solution as the result of a chemical reaction.
Precipitation Reaction
Stoichiometry & Chemical Reactions
Dimensionless
A reaction in which two solutions combine to form an insoluble solid that separates from the mixture.
A⁺(aq) + B⁻(aq) → AB(s)
Precipitation Titration
Analytical Chemistry & Spectroscopy
mol/L
A titration in which the analyte and titrant combine to form an insoluble product.
Ag⁺ + Cl⁻ → AgCl(s)
Precision
Foundations of Chemistry
Dimensionless
The closeness of repeated measurements of the same quantity to one another, regardless of their accuracy.
RSD = (s / x̄) × 100
Predicting Precipitation
Chemical Equilibrium
Dimensionless
The use of the ionic product and solubility product to decide whether a solid will form on mixing two solutions.
Q_sp > Ksp → precipitate
Pressure Equilibrium Constant
Chemical Equilibrium
Various
The equilibrium constant for a gaseous reaction expressed in terms of partial pressures.
Kp = p_C^c p_D^d / p_A^a p_B^b
Primary Cell
Electrochemistry & Redox
V
A cell in which the electrode reaction is irreversible, so it cannot be recharged.
Primary Standard
Analytical Chemistry & Spectroscopy
g/mol
A highly pure, stable substance that can be weighed accurately and used directly to prepare a solution of known concentration.
Primary Structure
Biochemistry & Polymer Chemistry
Dimensionless
The linear sequence of amino acids in a polypeptide chain.
Primary Valence
Inorganic & Coordination Chemistry
Dimensionless
In Werner's theory, the ionisable valence of a metal, equal to its oxidation state and satisfied by negative ions.
Principal Quantum Number
Atomic Structure & Periodicity
Dimensionless
The quantum number n that specifies the main energy level and average distance of an electron from the nucleus.
E_n = −13.6 Z² / n² eV