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5B10.81
Metalloids (Semimetals)solid at STPP-block

Boron

Group: 13Period: 2Standard Atomic Weight: 10.81 u

Why is Boron in this position?

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

Group Assignment
Group 13

Placed in Group 13 because it possesses 3 valence electrons (2s² 2p¹).

Period Assignment
Period 2

Placed in Period 2 because its valence electrons reside in the n=2 shell.

Orbital Block
P-block

Belongs to the p-block because the differentiating electron enters a 2p orbital.

Chemical Category
Metalloids (Semimetals)

Classified as a metalloid due to its intermediate electrical conductivity, covalent network structure, and semiconductor properties.

Atomic Structure & Bohr Shell Model

Shell Distribution: [2, 3]

Bohr Atomic Shell Model(2, 3)

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

5 Protons (p⁺)6 Neutrons (n⁰)
KShell K: Electron 1 of 2Shell K: Electron 2 of 2LShell L: Electron 1 of 3Shell L: Electron 2 of 3Shell L: Electron 3 of 3BZ = 5

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):3 / 8 electrons (38%)
Aufbau Electron Configuration
1s² 2s² 2p¹

Neutral ground state configuration. Valence electrons: 3.

Atomic & Quantum Properties

Electronegativity (Pauling)2.04 Pauling
1st Ionization Energy800.6 kJ/mol
Electron Affinity-26.7 kJ/mol
Atomic Radius (empirical)87 pm
Common Oxidation States+3
Crystal StructureRhombohedral

Physical & Thermal Properties

Density at STP2.34 g/cm³
Melting Point2076 °C (2349 K)
Boiling Point3927 °C (4200 K)
Magnetic OrderingDiamagnetic
Discovery Year1808
Discovered ByJoseph Louis Gay-Lussac & Louis Jacques Thénard

Real-World Uses, Occurrence & Compounds

Major Industrial & Everyday Uses
  • Thermal-shock resistant Pyrex borosilicate laboratory glassware
  • Fiberglass insulation and structural composites
  • Nuclear control rods for absorbing thermal neutrons (Boron-10 isotope)
  • Super-hard cubic boron nitride abrasive cutting tools
Occurrence in Nature

Concentrated in arid evaporite playa lake deposits as borax, kernite, and ulexite.

Etymology & Name Origin

From Arabic 'buraq' or Persian 'burah' for the mineral borax

Important Chemical Compounds
H₃BO₃ (Boric acid)
Na₂B₄O₇·10H₂O (Borax)
B₂H₆ (Diborane)
BN (Boron nitride)
Interesting Chemical Facts
  • Cubic Boron Nitride (c-BN) is the second hardest material known, inferior only to diamond.
  • Diborane (B₂H₆) was pivotal in quantum chemistry by proving the existence of 3-center-2-electron 'banana' bonds.
  • Boron burns with an intense, vivid emerald-green flame often seen in theatrical pyrotechnics.
Safety & Handling Note

Elemental boron is generally non-toxic, but ingestible borates in high doses disrupt mammalian endocrine and reproductive systems.