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12Mg24.305
Alkaline Earth Metalssolid at STPS-block

Magnesium

Group: 2Period: 3Standard Atomic Weight: 24.305 u

Why is Magnesium in this position?

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

Group Assignment
Group 2

Belongs to Group 2 because it has 2 valence electrons in its outer s-orbital (3s²).

Period Assignment
Period 3

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

Orbital Block
S-block

Belongs to the s-block because its valence subshell is 3s.

Chemical Category
Alkaline Earth Metals

Classified as an alkaline earth metal due to its basic oxide and standard +2 cation oxidation state.

Atomic Structure & Bohr Shell Model

Shell Distribution: [2, 8, 2]

Bohr Atomic Shell Model(2, 8, 2)

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

12 Protons (p⁺)12 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 2Shell M: Electron 2 of 2MgZ = 12

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):2 / 18 electrons (11%)
Aufbau Electron Configuration
1s² 2s² 2p⁶ 3s²

Neutral ground state configuration. Valence electrons: 2.

Atomic & Quantum Properties

Electronegativity (Pauling)1.31 Pauling
1st Ionization Energy737.7 kJ/mol
Electron Affinity0 kJ/mol
Atomic Radius (empirical)145 pm
Common Oxidation States+2
Crystal StructureHCP

Physical & Thermal Properties

Density at STP1.738 g/cm³
Melting Point650 °C (923 K)
Boiling Point1091 °C (1363 K)
Magnetic OrderingParamagnetic
Discovery Year1755
Discovered ByJoseph Black

Real-World Uses, Occurrence & Compounds

Major Industrial & Everyday Uses
  • Ultra-lightweight structural magnesium alloys for automotive and aerospace components
  • Magnesium-based flares and pyrotechnics emitting intense white light
  • Antacid and laxative medicinal formulations (Milk of Magnesia)
  • Sacrificial anode protection for underground pipelines and ship hulls
Occurrence in Nature

Abundant in seawater as Mg²⁺ ions, and in mineral deposits of dolomite, magnesite, and carnallite.

Etymology & Name Origin

From Magnesia, a district in Thessaly, Greece

Important Chemical Compounds
MgO (Magnesia)
Mg(OH)₂ (Milk of Magnesia)
MgSO₄·7H₂O (Epsom salt)
MgCl₂ (Magnesium chloride)
Interesting Chemical Facts
  • Magnesium sits right at the center of the chlorophyll porphyrin ring, making it the linchpin of global photosynthesis.
  • When ignited in air, magnesium ribbon burns with a dazzling, blinding white flame exceeding 3,100 °C.
  • Magnesium is the eighth most abundant element in the Earth's crust and fourth in the Earth as a whole.
Safety & Handling Note

Magnesium metal shavings and powder are highly combustible and burn so fiercely they can dissociate water and CO₂, requiring Class D dry-powder fire extinguishers.