#51 / 118
51Sb121.76
Metalloids (Semimetals)solid at STPP-block

Antimony

Group: 15Period: 5Standard Atomic Weight: 121.76 u

Why is Antimony in this position?

Understanding the scientific rationale behind Antimony's position in the periodic table:

Group Assignment
Group 15

Belongs to Group 15 (Pnictogens) because it has 5 valence electrons (5s² 5p³).

Period Assignment
Period 5

Belongs to Period 5 because its outermost electrons fill the n=5 shell.

Orbital Block
P-block

Belongs to the p-block because its differentiating electrons occupy 5p orbitals.

Chemical Category
Metalloids (Semimetals)

Classified as a metalloid due to its semi-metallic luster, brittle mechanical behavior, and moderate electrical conductivity.

Atomic Structure & Bohr Shell Model

Shell Distribution: [2, 8, 18, 18, 5]

Bohr Atomic Shell Model(2, 8, 18, 18, 5)

Hover or tap any shell orbit ring to inspect electron counts and 2n² capacities.

51 Protons (p⁺)71 Neutrons (n⁰)
KShell K: Electron 1 of 2Shell K: Electron 2 of 2LShell L: Electron 1 of 8Shell L: Electron 2 of 8Shell L: Electron 3 of 8Shell L: Electron 4 of 8Shell L: Electron 5 of 8Shell L: Electron 6 of 8Shell L: Electron 7 of 8Shell L: Electron 8 of 8MShell M: Electron 1 of 18Shell M: Electron 2 of 18Shell M: Electron 3 of 18Shell M: Electron 4 of 18Shell M: Electron 5 of 18Shell M: Electron 6 of 18Shell M: Electron 7 of 18Shell M: Electron 8 of 18Shell M: Electron 9 of 18Shell M: Electron 10 of 18Shell M: Electron 11 of 18Shell M: Electron 12 of 18Shell M: Electron 13 of 18Shell M: Electron 14 of 18Shell M: Electron 15 of 18Shell M: Electron 16 of 18Shell M: Electron 17 of 18Shell M: Electron 18 of 18NShell N: Electron 1 of 18Shell N: Electron 2 of 18Shell N: Electron 3 of 18Shell N: Electron 4 of 18Shell N: Electron 5 of 18Shell N: Electron 6 of 18Shell N: Electron 7 of 18Shell N: Electron 8 of 18Shell N: Electron 9 of 18Shell N: Electron 10 of 18Shell N: Electron 11 of 18Shell N: Electron 12 of 18Shell N: Electron 13 of 18Shell N: Electron 14 of 18Shell N: Electron 15 of 18Shell N: Electron 16 of 18Shell N: Electron 17 of 18Shell N: Electron 18 of 18OShell O: Electron 1 of 5Shell O: Electron 2 of 5Shell O: Electron 3 of 5Shell O: Electron 4 of 5Shell O: Electron 5 of 5SbZ = 51

Educational Note: This Niels Bohr planetary model visually illustrates principal quantum energy shells ($n=1, 2, 3\dots$) and electron counts. In modern quantum mechanics (Schrödinger model), electrons do not orbit in fixed circular planetary tracks, but exist as 3D probability clouds (orbitals: $s, p, d, f$) governed by the Heisenberg uncertainty principle.

Electron Shell Filling Breakdown

Shell K (n=1):2 / 2 electrons (100%)
Shell L (n=2):8 / 8 electrons (100%)
Shell M (n=3):18 / 18 electrons (100%)
Shell N (n=4):18 / 32 electrons (56%)
Shell O (n=5):5 / 50 electrons (10%)
Aufbau Electron Configuration
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p³

Neutral ground state configuration. Valence electrons: 5.

Atomic & Quantum Properties

Electronegativity (Pauling)2.05 Pauling
1st Ionization Energy834 kJ/mol
Electron Affinity-103.2 kJ/mol
Atomic Radius (empirical)133 pm
Common Oxidation States+3, +5, -3
Crystal StructureRhombohedral

Physical & Thermal Properties

Density at STP6.70 g/cm³
Melting Point630.63 °C (903.78 K)
Boiling Point1587 °C (1860 K)
Magnetic OrderingDiamagnetic
Discovery YearAncient
Discovered ByKnown to ancients; described by Vannoccio Biringuccio (1540)

Real-World Uses, Occurrence & Compounds

Major Industrial & Everyday Uses
  • Antimony trioxide (Sb₂O₃) flame retardant synergist in plastics and upholstery
  • Lead-acid car battery grid strengthening alloy (antimonial lead)
  • Polyethylene terephthalate (PET) plastic bottle polymerization catalyst
  • Phase-change memory (PRAM) materials for high-speed digital computing
Occurrence in Nature

Mined predominantly from stibnite ore (antimony trisulfide / Sb₂S₃), with over 70% of world supply sourced from China.

Etymology & Name Origin

From Greek 'anti-monos' (not alone); symbol Sb from Latin 'stibium' (kohl eye makeup)

Important Chemical Compounds
Sb₂O₃ (Antimony trioxide)
Sb₂S₃ (Stibnite)
SbF₅ (Antimony pentafluoride / Superacid component)
Interesting Chemical Facts
  • Antimony is one of the rare substances (along with water, bismuth, and silicon) that expands as it freezes from a liquid into a solid.
  • Fluoroantimonic acid (HSbF₆), made with antimony pentafluoride, is a superacid 20 quintillion times stronger than 100% pure sulfuric acid.
  • Queen Nefertiti and ancient Egyptians used ground stibnite (stibium / kohl) as cosmetic black eyeliner.
Safety & Handling Note

Toxic and irritating; antimony toxicity mirrors arsenic poisoning by disrupting cellular enzyme sulfhydryl groups.