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13Al26.982
Post-Transition Metalssolid at STPP-block

Aluminium

Group: 13Period: 3Standard Atomic Weight: 26.982 u

Why is Aluminium in this position?

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

Group Assignment
Group 13

Belongs to Group 13 because it has 3 valence electrons (3s² 3p¹).

Period Assignment
Period 3

Belongs to Period 3 because its valence electrons populate the n=3 shell.

Orbital Block
P-block

Belongs to the p-block because its differentiating electron enters the 3p subshell.

Chemical Category
Post-Transition Metals

Classified as a post-transition metal due to its ductile metallic nature combined with amphoteric chemical behavior.

Atomic Structure & Bohr Shell Model

Shell Distribution: [2, 8, 3]

Bohr Atomic Shell Model(2, 8, 3)

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

13 Protons (p⁺)14 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 3Shell M: Electron 2 of 3Shell M: Electron 3 of 3AlZ = 13

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):3 / 18 electrons (17%)
Aufbau Electron Configuration
1s² 2s² 2p⁶ 3s² 3p¹

Neutral ground state configuration. Valence electrons: 3.

Atomic & Quantum Properties

Electronegativity (Pauling)1.61 Pauling
1st Ionization Energy577.5 kJ/mol
Electron Affinity-42.5 kJ/mol
Atomic Radius (empirical)118 pm
Common Oxidation States+3
Crystal StructureFCC

Physical & Thermal Properties

Density at STP2.70 g/cm³
Melting Point660.32 °C (933.47 K)
Boiling Point2470 °C (2743 K)
Magnetic OrderingParamagnetic
Discovery Year1825
Discovered ByHans Christian Ørsted

Real-World Uses, Occurrence & Compounds

Major Industrial & Everyday Uses
  • Aircraft airframes, modern high-speed trains, and automotive chassis
  • High-voltage electrical transmission overhead cables
  • Recyclable beverage cans and culinary aluminium foil wrapping
  • Architectural window framing, solar panel frames, and skyscrapers
Occurrence in Nature

Third most abundant element in Earth's crust, mined primarily from bauxite ore processed via the Hall-Héroult electrolytic process.

Etymology & Name Origin

From Latin 'alumen' meaning alum mineral salt

Important Chemical Compounds
Al₂O₃ (Alumina / Corundum)
AlCl₃ (Aluminium chloride)
KAl(SO₄)₂·12H₂O (Potash alum)
Na₃AlF₆ (Cryolite)
Interesting Chemical Facts
  • Rubies and sapphires are actually crystalline aluminium oxide (corundum, Al₂O₃) tinted by trace chromium or iron/titanium impurities.
  • In the 19th century, aluminium was more precious than silver and gold; Napoleon III famously served VIP guests with aluminium cutlery.
  • Recycling aluminium saves 95% of the massive electrical energy required to produce it from raw bauxite ore.
Safety & Handling Note

Finely divided aluminium powder is flammable and forms explosive clouds with air; generally non-toxic as solid metal.