Chemistry terms starting with S

s-Block Elements Atomic Structure & Periodicity Dimensionless The elements of groups 1 and 2, plus helium, whose outermost electrons occupy an s orbital. ns¹ or ns²

Sacrificial Anode Electrochemistry & Redox Dimensionless A block of reactive metal attached to a structure so that it corrodes preferentially and protects the structure.

Salt Acids, Bases & Salts Dimensionless An ionic compound formed when the hydrogen of an acid is replaced by a metal or other cation. acid + base → salt + water

Salt Bridge Electrochemistry & Redox Dimensionless A conducting connection between the two half-cells of a galvanic cell that completes the circuit and maintains electrical neutrality.

Salt Hydrolysis Acids, Bases & Salts mol/L The reaction of a salt's ions with water to produce an acidic or alkaline solution. A⁻ + H₂O ⇌ HA + OH⁻

Sampling Analytical Chemistry & Spectroscopy g The process of selecting a small portion of material that genuinely represents the bulk being analysed.

Sandwich Compound Inorganic & Coordination Chemistry Dimensionless An organometallic compound in which a metal atom is held between two parallel planar cyclic ligands. e.g. Fe(C₅H₅)₂

Saponification Stoichiometry & Chemical Reactions Dimensionless The alkaline hydrolysis of an ester, particularly a triglyceride, to give a carboxylate salt and an alcohol. RCOOR′ + NaOH → RCOONa + R′OH

Saturated Fat Biochemistry & Polymer Chemistry Dimensionless A fat whose fatty acid chains contain only single carbon–carbon bonds.

Saturated Solution Solutions & Colligative Properties mol/L A solution in dynamic equilibrium with undissolved solute, containing the maximum amount that will dissolve at that temperature. rate dissolve = rate crystallise

Saturation and Unsaturation Organic Chemistry Dimensionless The distinction between compounds containing only single bonds and those containing multiple bonds or rings. DoU = (2C + 2 + N − H − X)/2

Schottky Defect States of Matter & Gas Laws Dimensionless A point defect in which equal numbers of cations and anions are missing from their lattice sites.

Schrödinger Wave Equation Atomic Structure & Periodicity J The fundamental equation of quantum mechanics whose solutions give the allowed energies and wavefunctions of a system. Ĥψ = Eψ

Scintillation Counter Nuclear & Radiochemistry counts/s A detector in which radiation causes a material to emit flashes of light that are counted and measured.

Second Law of Thermodynamics Thermochemistry & Thermodynamics J/K The total entropy of the universe increases in every spontaneous process. ΔS_universe > 0

Second-Order Reaction Chemical Kinetics & Catalysis L/(mol·s) A reaction whose rate depends on the square of one concentration or on the product of two concentrations. 1/[A] = 1/[A]₀ + kt

Secondary Cell Electrochemistry & Redox V A cell whose reaction can be reversed by an applied current, allowing it to be recharged and reused.

Secondary Standard Analytical Chemistry & Spectroscopy mol/L A solution whose concentration has been established by titration against a primary standard.

Secondary Structure Biochemistry & Polymer Chemistry Dimensionless Local regular folding patterns of a polypeptide backbone stabilised by hydrogen bonds.

Secondary Valence Inorganic & Coordination Chemistry Dimensionless In Werner's theory, the non-ionisable valence corresponding to the coordination number, satisfied by ligands in fixed spatial positions.

Secular Equilibrium Nuclear & Radiochemistry Bq The steady state reached when a long-lived parent supports a short-lived daughter at constant activity. λ₁N₁ = λ₂N₂

Selective Discharge Electrochemistry & Redox V The preferential reaction of one ion over others at an electrode during electrolysis.

Selective Precipitation Chemical Equilibrium mol/L The separation of ions from a mixture by adding a reagent that precipitates them one at a time.

Selectivity Chemical Kinetics & Catalysis Dimensionless The ability of a catalyst to direct a reaction towards one particular product among several possible ones. selectivity = desired product / total product

Terms starting with S