Periodic law and its systematic consequences: periodic-trend quantities (electronegativity, ionisation energy, electron affinity) and the group/period organisation that falls out of electron-configuration and effective nuclear charge.
periodic-table
Periodic law
Chemical and physical properties of the elements are periodic functions of their atomic number Z. Organises elements into groups (columns)…
Periodic table of the elements
Canonical tabular arrangement of the chemical elements by atomic number and recurring chemical properties, with blocks (s, p, d, f)…
Electronegativity (Pauling)
Dimensionless measure of an atom's tendency to attract bonding electrons. Defined empirically by Pauling from bond-dissociation energies.…
First ionisation energy
Energy required to remove the most loosely-bound electron from a neutral atom in the gas phase. Trends: increases across a period,…
Electron affinity
Energy released when a neutral gas-phase atom accepts an additional electron to form a singly-charged anion. Largest for halogens;…
Atomic radius trends
Decreases across period (↑Zeff), increases down group (↑n). Lanthanide contraction compresses post-Ln elements → Zr/Hf radii…
Superheavy elements (Z>103)
Transactinides produced by cold/hot fusion at JINR, GSI, RIKEN. Oganesson (118) completes period 7. Relativistic effects predict deviations…
Relativistic effects in chemistry
Inner-shell electrons approach c for heavy atoms → mass increase + orbital contraction. Explains Au color, Hg liquid, Pb stability of +2,…
Oxidation state (formal assignment)
Hypothetical charge if bonds fully heterolytic toward more-EN partner. IUPAC 2014: Br2 0, H₂O ₂H+1 O-2. Group-oxidation-state maxima follow…
HSAB principle (Pearson)
Hard acids (Li+, Al³⁺, H+) prefer hard bases (F⁻, O²⁻); soft acids (Hg²⁺, Au+, Pt²⁺) prefer soft bases (I⁻, R₂S, PR₃). Rationalizes complex…
Lanthanide contraction
4f shielding poor → Z_eff increases across Ln; 5d elements smaller than expected; explains Zr ≈ Hf radii, Au vs Ag noble-metal chemistry.
Actinide contraction
Analogous 5f-based contraction but smaller due to earlier relativistic effects; differentiates An from Ln chemistry.
Diagonal relationships (Li/Mg, Be/Al, B/Si)
Similar chemistry along periodic-table diagonal from compensation between size and charge; Li carbonate decomposes like Mg's.
Inert pair effect
Tl(I), Pb(II), Bi(III) favored over group max for heavy p-block due to poor hybridization with 6s²; relativistic stabilization.
Relativistic effects in chemistry
6s contraction and 5d expansion in Au, Hg; Hg liquid, Au color, high Pb density; from Dirac equation for inner electrons.
Secondary (Biron) periodicity
Non-monotonic trends in groups 13-17 due to d-block insertion and inert-pair; Ga smaller than Al.
Electron affinity anomalies
EA(F) < EA(Cl) due to compact 2p and e-e repulsion; EA of noble gases ≤ 0; EA of group 15 anomalously low.
Oxidation state periodicity
Group max state = group number (G 1-7); variable d-block from d^n partial fillings; Frost diagram visualizes stabilities.
Madelung (n+ℓ) rule
Orbitals fill by increasing n+ℓ, lowest n on ties; explains 4s before 3d filling; exceptions Cr, Cu.
Noble gas chemistry
XeF₂, XeO₄, XePtF₆ (Bartlett 1962); Kr, Ar, He compounds only under extreme conditions; high 1st IE but polarizable.
Superheavy element chemistry
Expected relativistic deviations from group trends for Cn, Fl, Og; single-atom gas-phase chemistry experiments at GSI, JINR.
Extended periodic table (g-block)
Predicted 8th period g-block (5g) from Z=121; beyond island of stability; purely theoretical.
Period length 2n^2 rule from Pauli-exclusion shell filling (periodic-table)
Chemistry application of L1 pauli-exclusion and angular-momentum-quantum. The maximum electron occupancy of principal shell n is 2 n^2,…
Koopmans' theorem: first ionization energy from Hartree-Fock HOMO energy (periodic-table)
Chemistry application of L1 slater-determinant-atomic and hartree-fock-iteration-atomic. Koopmans' theorem (1934) states that within the…