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960 terms · page 27 of 40
Nuclear Stability
Nuclear & Radiochemistry
Dimensionless
The tendency of a nucleus to persist without undergoing radioactive decay.
Nucleic Acid
Biochemistry & Polymer Chemistry
Dimensionless
A biopolymer of nucleotides that stores and transmits genetic information.
Nucleophile
Organic Chemistry
Dimensionless
An electron-rich species that donates a pair of electrons to form a new covalent bond.
Nu⁻ or Nu:
Nucleophilic Substitution
Organic Chemistry
Dimensionless
A reaction in which a nucleophile replaces a leaving group attached to a saturated carbon.
Nu⁻ + R–X → R–Nu + X⁻
Nucleotide
Biochemistry & Polymer Chemistry
Dimensionless
The monomer of nucleic acids, consisting of a nitrogenous base, a five-carbon sugar and a phosphate group.
Nucleus
Atomic Structure & Periodicity
m
The dense, positively charged core of an atom, containing virtually all of its mass in protons and neutrons.
r ≈ 1.2 × A^(1/3) fm
Nuclide
Nuclear & Radiochemistry
Dimensionless
A distinct species of atom characterised by a specific number of protons and neutrons in its nucleus.
ᴬ_Z X
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