Chemistry terms starting with O

Octahedral Geometry Chemical Bonding & Molecular Structure degrees A shape with six bonded atoms at the vertices of a regular octahedron, all bond angles being 90° or 180°. AX₆

Octahedral Splitting Inorganic & Coordination Chemistry cm⁻¹ The division of the five d orbitals into a lower t₂g set of three and an upper e_g set of two under an octahedral ligand field. t₂g (−0.4Δ₀), e_g (+0.6Δ₀)

Octet Rule Chemical Bonding & Molecular Structure Dimensionless The observation that atoms tend to gain, lose or share electrons until they are surrounded by eight valence electrons.

Odd-Electron Molecule Chemical Bonding & Molecular Structure Dimensionless A species containing an unpaired electron, so that its total electron count is odd and no octet structure is possible.

Open System Thermochemistry & Thermodynamics Dimensionless A system that can exchange both energy and matter with its surroundings.

Optical Activity Organic Chemistry degrees The ability of a substance to rotate the plane of polarised light passing through it. [α] = α / (l × c)

Optical Isomerism Organic Chemistry degrees Stereoisomerism in which molecules are non-superimposable mirror images and rotate plane-polarised light in opposite directions.

Optical Isomerism in Complexes Inorganic & Coordination Chemistry degrees The existence of non-superimposable mirror-image forms of a coordination compound. Δ and Λ

Optimum Conditions for Industrial Yield Chemical Equilibrium Various The compromise set of temperature, pressure and catalyst chosen to balance equilibrium yield against reaction rate and cost.

Order of Reaction Chemical Kinetics & Catalysis Dimensionless The power to which the concentration of a given reactant is raised in the experimentally determined rate law. rate ∝ [A]^m

Ore Inorganic & Coordination Chemistry Dimensionless A naturally occurring mineral deposit from which a metal can be extracted profitably.

Organic Chemistry Organic Chemistry Dimensionless The study of the structure, properties, composition and reactions of carbon-containing compounds.

Organometallic Compound Inorganic & Coordination Chemistry Dimensionless A compound containing at least one direct bond between a metal and a carbon atom. M–C

Osmosis Solutions & Colligative Properties Dimensionless The net movement of solvent molecules through a semipermeable membrane from a dilute to a concentrated solution.

Osmotic Pressure Solutions & Colligative Properties atm The external pressure that must be applied to a solution to prevent the inward flow of solvent through a semipermeable membrane. π = i M R T

Ostwald's Dilution Law Acids, Bases & Salts mol/L The relation showing how the degree of ionisation of a weak electrolyte increases on dilution. Ka = cα² / (1 − α)

Outlier Test Analytical Chemistry & Spectroscopy Dimensionless A statistical procedure for deciding whether a suspect result differs enough from the others to be rejected. Q = |suspect − nearest| / range

Overall Formation Constant Chemical Equilibrium Various The equilibrium constant for the formation of a complex directly from the free metal ion and all its ligands. β_n = K₁K₂ … K_n

Overall Order Chemical Kinetics & Catalysis Dimensionless The sum of the individual orders with respect to every reactant appearing in the rate law. n = m₁ + m₂ + …

Overpotential Electrochemistry & Redox V The extra voltage beyond the theoretical value that must be applied before an electrode reaction proceeds at a useful rate. η = E_applied − E_equilibrium

Oxidation Electrochemistry & Redox Dimensionless The loss of electrons by a species, accompanied by an increase in its oxidation number. M → Mⁿ⁺ + n e⁻

Oxidation Number Electrochemistry & Redox Dimensionless The hypothetical charge an atom would carry if all its bonds were treated as fully ionic. Σ oxidation numbers = overall charge

Oxidation Number Method Stoichiometry & Chemical Reactions Dimensionless A technique for balancing redox equations by equating the total increase and decrease in oxidation numbers. Σ increase = Σ decrease

Oxidation of Alcohols Organic Chemistry Dimensionless The conversion of alcohols to carbonyl compounds or carboxylic acids by removal of hydrogen. R–CH₂OH → RCHO → RCOOH

Terms starting with O