The atomic mass of magnesium (Mg) is 24 u (atomic mass units), more precisely 24.305 u. The atomic number of magnesium is 12, meaning it has 12 protons. Magnesium is a Group 2 (alkaline earth metal) element in Period 3 of the periodic table. It has the electronic configuration 2, 8, 2 (or [Ne] 3s²) and forms Mg²⁺ ions by losing 2 electrons.
Atomic mass of Magnesium (Mg) = 24 u (precisely 24.305 u).
Atomic number of Mg = 12 (12 protons).
Electronic configuration: 2, 8, 2 → valency = 2 → forms Mg²⁺.
Group 2 (Alkaline Earth Metal), Period 3, s-block.
Most abundant isotope: Mg-24 (78.99%).
Mg burns with a brilliant white flame — used in flares and fireworks.
Mg(OH)₂ = Milk of Magnesia — antacid.
Number of neutrons in Mg-24 = 24 − 12 = 12.
Symbol: Mg Atomic Number: 12 Atomic Mass: 24 u (standard: 24.305 u) Group: 2 (Alkaline Earth Metals) Period: 3 Block: s-block Electronic Configuration: 2, 8, 2 (or [Ne] 3s²) Valency: 2 (Mg²⁺) Physical state: Solid (silvery-white metal)
Number of subatomic particles in most common isotope (Mg-24): • Protons: 12 • Neutrons: 12 (= mass number − atomic number = 24 − 12) • Electrons: 12 (in neutral atom)
Ion formation: Mg → Mg²⁺ + 2e⁻ • Mg²⁺ has 10 electrons (12 − 2 = 10) • Electronic config of Mg²⁺: 2, 8 (neon configuration)
Magnesium has three naturally occurring stable isotopes:
Isotope | Mass Number | Abundance Mg-24 (²⁴Mg) | 24 | ~78.99% Mg-25 (²⁵Mg) | 25 | ~10.00% Mg-26 (²⁶Mg) | 26 | ~11.01%
Average atomic mass calculation: = (24 × 0.7899) + (25 × 0.1000) + (26 × 0.1101) = 18.958 + 2.500 + 2.863 = 24.321 ≈ 24.305 u (standard accepted value)
For school/exam purposes: Atomic mass of Mg = 24 u
Mg-24 is the most abundant isotope (≈79%), so the atomic mass is close to 24.
Important reactions of Magnesium:
Burning in air: Mg + O₂ → MgO (Magnesium oxide — brilliant white flame) 2Mg + O₂ → 2MgO • Mg burns with an intense white light — used in flares and fireworks • Note: Mg also reacts with N₂: 3Mg + N₂ → Mg₃N₂
Reaction with water: • Cold water: slow/no reaction • Hot water: Mg + H₂O → MgO + H₂↑ • Steam: faster reaction
Reaction with acids: Mg + H₂SO₄ → MgSO₄ + H₂↑ Mg + 2HCl → MgCl₂ + H₂↑
Uses of Magnesium: • In alloys: Duralumin (Al-Mg alloy) — lightweight, strong • In fireworks and signal flares (bright white flame) • In flash bulbs for photography • In antacids: Mg(OH)₂ (Milk of Magnesia) — treats acidity • Magnesium carbonate (MgCO₃) — used by gymnasts/weightlifters for grip • Essential mineral for the human body (chlorophyll contains Mg²⁺)
The atomic mass of magnesium (Mg) is 24 u (or more precisely, 24.305 u). This value is the weighted average of its three naturally occurring isotopes: Mg-24 (78.99%), Mg-25 (10%), and Mg-26 (11%). For school-level calculations, atomic mass of Mg = 24 u is used.
Atomic number of Mg = 12 (12 protons). Atomic mass of Mg = 24 u. It has 12 neutrons in its most abundant isotope (Mg-24). Electronic configuration: 2, 8, 2. Valency = 2 (forms Mg²⁺ by losing 2 electrons).
Magnesium (Mg) has 12 protons (atomic number = 12). In its most common isotope Mg-24: neutrons = mass number − atomic number = 24 − 12 = 12 neutrons. So Mg-24 has 12 protons and 12 neutrons.
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