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15P30.974
Reactive Nonmetalssolid at STPP-block

Phosphorus

Group: 15Period: 3Standard Atomic Weight: 30.974 u

Why is Phosphorus in this position?

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

Group Assignment
Group 15

Belongs to Group 15 because it has 5 valence electrons (3s² 3p³).

Period Assignment
Period 3

Belongs to Period 3 because its outermost electrons occupy principal shell n=3.

Orbital Block
P-block

Belongs to the p-block because its valence electrons occupy 3p orbitals.

Chemical Category
Reactive Nonmetals

Classified as a reactive nonmetal due to its low electrical conductivity and characteristic covalent network allotropy.

Atomic Structure & Bohr Shell Model

Shell Distribution: [2, 8, 5]

Bohr Atomic Shell Model(2, 8, 5)

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

15 Protons (p⁺)16 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 5Shell M: Electron 2 of 5Shell M: Electron 3 of 5Shell M: Electron 4 of 5Shell M: Electron 5 of 5PZ = 15

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):5 / 18 electrons (28%)
Aufbau Electron Configuration
1s² 2s² 2p⁶ 3s² 3p³

Neutral ground state configuration. Valence electrons: 5.

Atomic & Quantum Properties

Electronegativity (Pauling)2.19 Pauling
1st Ionization Energy1011.8 kJ/mol
Electron Affinity-72 kJ/mol
Atomic Radius (empirical)98 pm
Common Oxidation States+5, +3, -3
Crystal StructureMonoclinic / Orthorhombic

Physical & Thermal Properties

Density at STP1.82 g/cm³ (white)
Melting Point44.15 °C (317.3 K)
Boiling Point280.5 °C (553.7 K)
Magnetic OrderingDiamagnetic
Discovery Year1669
Discovered ByHennig Brand

Real-World Uses, Occurrence & Compounds

Major Industrial & Everyday Uses
  • Agricultural NPK fertilizers providing essential soil phosphorus
  • Safety matches and pyrotechnics (Red phosphorus)
  • Food-grade acidulant in cola drinks (Phosphoric acid)
  • Industrial water softeners, rust removers, and flame retardants
Occurrence in Nature

Found predominantly in phosphate rock minerals such as apatite (Ca₅(PO₄)₃(F,Cl,OH)).

Etymology & Name Origin

From Greek 'phosphoros' meaning light-bringer (the morning star Venus)

Important Chemical Compounds
H₃PO₄ (Phosphoric acid)
Ca₃(PO₄)₂ (Calcium phosphate)
P₄O₁₀ (Phosphorus pentoxide)
PCl₅ (Phosphorus pentachloride)
Interesting Chemical Facts
  • Hennig Brand discovered phosphorus in 1669 while boiling down human urine in a quest to synthesize the Philosopher's Stone.
  • White phosphorus glows eerily in the dark due to chemiluminescence (reacting with atmospheric oxygen), producing the term 'phosphorescence'.
  • Adenosine triphosphate (ATP) is the universal biological energy currency in every living organism on Earth.
Safety & Handling Note

White phosphorus is acutely toxic and spontaneously ignites in air at 30 °C; red phosphorus is much safer and non-pyrophoric.