Chemistry terms starting with P

p-Block Elements Atomic Structure & Periodicity Dimensionless The elements of groups 13 to 18, in which the outermost electrons progressively fill p orbitals. ns² np¹⁻⁶

Packing Efficiency States of Matter & Gas Laws Dimensionless The percentage of the total volume of a unit cell that is actually occupied by the constituent particles. (volume of atoms / cell volume) × 100

Paramagnetism Atomic Structure & Periodicity BM Weak attraction into a magnetic field, shown by substances containing one or more unpaired electrons. μ = √(n(n+2)) BM

Parent and Daughter Nuclide Nuclear & Radiochemistry Dimensionless The nuclide undergoing decay and the nuclide produced by that decay. parent → daughter + radiation

Partial Pressure States of Matter & Gas Laws Pa The pressure that one component of a gas mixture would exert if it alone occupied the whole volume. p_i = x_i × p_total

Partition Coefficient Chemical Equilibrium Dimensionless The equilibrium ratio of a solute's concentrations in two immiscible phases. P = C₁ / C₂

Parts per Billion Solutions & Colligative Properties ppb A concentration unit expressing one part of solute per thousand million parts of solution. ppb = (m_solute / m_solution) × 10⁹

Parts per Million Solutions & Colligative Properties ppm A concentration unit expressing one part of solute per million parts of solution by mass or volume. ppm = (m_solute / m_solution) × 10⁶

Path Function Thermochemistry & Thermodynamics J A quantity whose value depends on the specific route taken between two states. δq, δw

Pauli Exclusion Principle Atomic Structure & Periodicity Dimensionless The rule that no two electrons in an atom may have the same set of all four quantum numbers. n, l, mₗ, mₛ must differ

Penetrating Power Nuclear & Radiochemistry mm The depth to which a given type of radiation can travel into a material before being absorbed.

Peptide Bond Biochemistry & Polymer Chemistry Dimensionless The amide linkage joining the carboxyl group of one amino acid to the amino group of the next. –CO–NH–

Percentage Composition Foundations of Chemistry Dimensionless The proportion by mass of each element in a compound, expressed as a percentage of the total mass. % element = (n × A_r / M_r) × 100

Percentage Purity Stoichiometry & Chemical Reactions Dimensionless The proportion of a sample that consists of the desired compound, expressed as a percentage of the total mass. % purity = (mass pure / mass sample) × 100

Percentage Yield Stoichiometry & Chemical Reactions Dimensionless The actual yield expressed as a percentage of the theoretical yield. % yield = (actual / theoretical) × 100

Period Atomic Structure & Periodicity Dimensionless A horizontal row of the periodic table, corresponding to one principal quantum number of the valence shell.

Periodic Law Atomic Structure & Periodicity Dimensionless The principle that the properties of the elements are periodic functions of their atomic numbers.

Periodic Table Atomic Structure & Periodicity Dimensionless The tabular arrangement of the chemical elements by increasing atomic number, grouping those with similar properties in vertical columns.

Perturbation and Re-equilibration Chemical Equilibrium s The disturbance of an equilibrium followed by its relaxation to a new equilibrium state.

pH Acids, Bases & Salts Dimensionless The negative logarithm to base ten of the hydrogen ion concentration, measuring the acidity of a solution. pH = −log[H⁺]

pH Scale Acids, Bases & Salts Dimensionless The conventional scale, usually running from 0 to 14, on which the acidity or alkalinity of aqueous solutions is expressed. 0 (acidic) – 7 (neutral) – 14 (alkaline)

Phase Diagram States of Matter & Gas Laws Pa, K A pressure–temperature plot showing which phase of a substance is thermodynamically stable under any given conditions.

Phase Equilibrium Chemical Equilibrium Dimensionless The condition in which two or more phases of a substance coexist with no net transfer between them. μ_phase1 = μ_phase2

Phenol Organic Chemistry Dimensionless A compound in which a hydroxyl group is bonded directly to an aromatic ring. C₆H₅–OH

Terms starting with P