Chemistry terms starting with D

d-Block Elements Atomic Structure & Periodicity Dimensionless The elements of groups 3 to 12, whose valence electrons fill d orbitals of the penultimate shell. (n−1)d¹⁻¹⁰ ns⁰⁻²

Dalton's Atomic Theory Foundations of Chemistry Dimensionless The 1808 model proposing that elements consist of indivisible atoms that are identical within an element and combine in fixed whole-number ratios.

Dalton's Law of Partial Pressures States of Matter & Gas Laws Pa The total pressure of a gas mixture equals the sum of the pressures each component would exert alone in the same volume. p_total = p₁ + p₂ + p₃ …

Daniell Cell Electrochemistry & Redox V The classic galvanic cell consisting of a zinc electrode in zinc sulfate and a copper electrode in copper sulfate. Zn + Cu²⁺ → Zn²⁺ + Cu, E° = 1.10 V

de Broglie Relation Atomic Structure & Periodicity m The relation stating that every particle has an associated wavelength inversely proportional to its momentum. λ = h / mv

Debye–Hückel Limiting Law Chemical Equilibrium Dimensionless The theoretical relation predicting activity coefficients of ions in very dilute solution from their charge and the ionic strength. log γ = −A z² √I

Decantation Foundations of Chemistry Dimensionless The separation of a liquid from a settled solid or a denser immiscible liquid by carefully pouring off the upper layer.

Decay Constant Nuclear & Radiochemistry s⁻¹ The probability per unit time that a given nucleus will decay. λ = 0.693 / t½

Decomposition Potential Electrochemistry & Redox V The minimum voltage that must be applied to an electrolytic cell before continuous electrolysis begins.

Decomposition Reaction Stoichiometry & Chemical Reactions Dimensionless A reaction in which a single compound breaks down into two or more simpler substances. AB → A + B

Degenerate Orbitals Atomic Structure & Periodicity Dimensionless Two or more orbitals in the same atom that have exactly the same energy.

Degree of Dissociation Chemical Equilibrium Dimensionless The fraction of the original substance that has broken apart at equilibrium. α = amount dissociated / initial amount

Degree of Hydrolysis Acids, Bases & Salts Dimensionless The fraction of a salt's ions that have reacted with water at equilibrium. h = √(Kh / c)

Degree of Ionisation Acids, Bases & Salts Dimensionless The fraction of dissolved electrolyte molecules that have broken into ions at equilibrium. α = ionised / total

Degree of Polymerisation Biochemistry & Polymer Chemistry Dimensionless The number of monomer units in an average polymer chain. DP = M_polymer / M_monomer

Dehydration Reaction Stoichiometry & Chemical Reactions Dimensionless A reaction in which water is removed from a single molecule, generally producing an unsaturated or condensed product. R–CH₂–CH₂OH → R–CH=CH₂ + H₂O

Deliquescence Foundations of Chemistry Dimensionless The property of a solid that absorbs enough water vapour from the air to dissolve completely in the water it takes up.

Delocalisation Chemical Bonding & Molecular Structure Dimensionless The spreading of electrons over three or more atoms rather than their confinement between two.

Denaturation Biochemistry & Polymer Chemistry Dimensionless The loss of a protein's native three-dimensional structure without breaking its peptide bonds.

Density Foundations of Chemistry g/cm³ The mass of a substance contained in a unit volume, a characteristic intensive property of each material. ρ = m / V

Denticity Inorganic & Coordination Chemistry Dimensionless The number of donor atoms a single ligand uses to bind to one metal centre. κⁿ or ηⁿ notation

Deposition States of Matter & Gas Laws kJ/mol The direct conversion of a vapour into a solid without an intermediate liquid phase.

Diagonal Relationship Atomic Structure & Periodicity Dimensionless The similarity in properties between an element of period 2 and the element one place to its lower right in period 3.

Diamagnetism Atomic Structure & Periodicity BM Weak repulsion from a magnetic field, shown by substances in which all electrons are spin-paired. μ = 0 BM

Terms starting with D