MAGNÉSIO

Introdução

Número atômico: 12
Grupo: 2 or II A
Peso atômico: 24.305
Período: 3
Número CAS: 7439-95-4

Classificação

Calcogênio
halogênio
Gás nobre
Lantanóides
Actinóide
Terra-rara
Platinum Metal Group
Transuranium
Não Isótopos Estáveis
Sólido
Líquido
Gás
Sólido (previsto)

Descrição • Usos / Função

Compounds of magnesium have long been known. Black recognized magnesium as an element in 1755. It was isolated by Davy in 1808, and prepared in coherent form by Bussy in 1831. Magnesium is the eighth most abundant element in the earth’s crust. It does not occur uncombined, but is found in large deposits in the form of magnesite, dolomite, and other minerals. The metal is now principally obtained in the U.S. by electrolysis of fused magnesium chloride derived from brines, wells, and sea water. Magnesium is a light, silvery-white, and fairly tough metal. It tarnishes slightly in air, and finely divided magnesium readily ignites upon heating in air and burns with a dazzling white flame. It is used in flashlight photography, flares, and pyrotechnics, including incendiary bombs. It is one third lighter than aluminium, and in alloys is essential for airplane and missile contruction. The metal improves the mechanical, fabrication, and welding characteristics of aluminum when used as an alloying agent. Magnesium is used in producing nodular graphite in cast iron,and is used as an additive to conventional propellants. It is also used as a reducing agent in the production of pure uranium and other metals from their salts. The hydroxide (milk of magnesia), chloride, sulfate (Epsom salts), and citrate are used in medicine. Dead-burned magnesite is employed for refractory purposes such as brick and liners in furnaces and converters. Organic magnesium compounds (Grignard’s reagents) are important. Magnesium is an important element in both plant and animal life. Chlorophylls are magnesium-centered porphyrins. The adult daily requirement of magnesium is about 300 mg/day, but this is affected by various factors. Great care should be taken in handling magnesium metal, especially in the finely divided state, as serious fires can occur. Water should not be used on burning magnesium or on magnesium fires. Natural magnesium contains three isotopes. Twelve other isotopes are recognized. Magnesium metal costs about $170/kg (99.99%). 1

• "(as the Mg2+ ion) plays a vital role in metabolism and muscle functions" 2
• "commonly used to produce the bright light for photographic flash units" 3
• "is a useful structural material, especially if alloyed with aluminum" 4
• "alloys having more magnesium than aluminum are used when a high strength-to-weight ratio is needed and when corrosion resistance is important, such as in aircraft and automotive parts and in lightweight tools" 5
• "It has been suggested that magnesium, an essential component in chlorophyll, is removed from pine needles by the combined effects of ozone and acids...Another harmful effect of acid rain may be that it leaches essential metal ions such as Ca2+ and Mg2+ from soil as soluble salts." 6
• "The tires on the Hummer vehicles used in the Gulf War were made blowout-proof by strong, lightweight magnesium inserts....used in photographic flash accessories and fireworks. It is very lightweight and is currently used in many alloys for building materials." 7
• "used in lightweight alloys...Mg compounds find applications in the pharmaceutical and chemical process industries." 8

Propriedades físicas

Ponto de fusão:9*  650 °C = 923.15 K = 1202 °F
Ponto de ebulição:9* 1090 °C = 1363.15 K = 1994 °F
Ponto de sublimação:9 
Ponto Triplo:9 
Ponto crítico:9 
Densidade:10  1.74 g/cm3

* - at 1 atm

Configuração Electron

Configuração Electron: [Ne] 3s2
Quadra: s
Mais alto nível de energia Ocupado: 3
Elétrons de valência: 2

Números quânticos:

n = 3
ℓ = 0
m = 0
ms = -½

Colagem

Eletronegatividade (escala Pauling):11 1.31
Electropositivity (escala Pauling): 2.69
Electron Affinity:12 not stable eV
oxidação Unidos: +2
Função no trabalho:13 3.66 eV = 5.86332E-19 J

potencial de ionização   eV 14  kJ/mol  
1 7.64624    737.7
2 15.03528    1450.7
3 80.1437    7732.7
4 109.2655    10542.5
potencial de ionização   eV 14  kJ/mol  
5 141.27    13630.5
6 186.76    18019.6
7 225.02    21711.1
8 265.96    25661.2
potencial de ionização   eV 14  kJ/mol  
9 328.06    31653.0
10 367.5    35458.4
11 1761.805    169988.3
12 1962.665    189368.3

Termoquímica

Calor específico: 1.023 J/g°C 15 = 24.864 J/mol°C = 0.245 cal/g°C = 5.943 cal/mol°C
Condutividade térmica: 156 (W/m)/K, 27°C 16
Calor de fusão: 8.954 kJ/mol 17 = 368.4 J/g
Calor da vaporização: 127.4 kJ/mol 18 = 5241.7 J/g
Estado da matéria Entalpia de formação (ΔHf°)19 entropia (S°)19 Gibbs Energia Livre (ΔGf°)19
(kcal/mol) (kJ/mol) (cal/K) (J/K) (kcal/mol) (kJ/mol)
(s) 0 0 7.814 32.693776 0 0
(ℓ) 2.16 9.03744 10.16 42.50944 1.46 6.10864
(g) 35.28 147.61152 35.50 148.532 27.03 113.09352

isótopos

nuclide Massa 20 Meia vida 20 spin nuclear 20 Energia de ligação
19Mg 19.03547(27) 1/2-# 111.36 MeV
20Mg 20.018863(29) 90.8(24) ms 0+ 135.27 MeV
21Mg 21.011713(18) 122(2) ms (5/2,3/2)+ 149.86 MeV
22Mg 21.9995738(14) 3.8755(12) s 0+ 169.11 MeV
23Mg 22.9941237(14) 11.317(11) s 3/2+ 181.84 MeV
24Mg 23.985041700(14) ESTÁVEL 0+ 198.30 MeV
25Mg 24.98583692(3) ESTÁVEL 5/2+ 206.37 MeV
26Mg 25.982592929(30) ESTÁVEL 0+ 217.23 MeV
27Mg 26.98434059(5) 9.458(12) min 1/2+ 223.44 MeV
28Mg 27.9838768(22) 20.915(9) h 0+ 232.44 MeV
29Mg 28.988600(15) 1.30(12) s 3/2+ 235.86 MeV
30Mg 29.990434(9) 335(17) ms 0+ 242.07 MeV
31Mg 30.996546(13) 230(20) ms 3/2+ 244.55 MeV
32Mg 31.998975(19) 86(5) ms 0+ 250.76 MeV
33Mg 33.005254(21) 90.5(16) ms 7/2-# 252.31 MeV
34Mg 34.00946(25) 20(10) ms 0+ 256.65 MeV
35Mg 35.01734(43)# 70(40) ms (7/2-)# 257.27 MeV
36Mg 36.02300(54)# 3.9(13) ms 0+ 259.75 MeV
37Mg 37.03140(97)# 40# ms [>260 ns] 7/2-# 260.37 MeV
38Mg 38.03757(54)# 1# ms [>260 ns] 0+ 262.86 MeV
39Mg 39.04677(55)# <260 ns 7/2-# 262.54 MeV
40Mg 40.05393(97)# 1# ms 0+ 264.10 MeV
Os valores marcados # não são puramente derivado a partir de dados experimentais, mas, pelo menos, parcialmente a partir de tendências sistemáticas. Gira com argumentos de atribuição fracos estão entre parênteses. 20

reações

Abundância

Terra - Os compostos de origem: carbonates/sulfates 26
Terra - A água do mar: 1290 mg/L 27
Terra -  crosta:  23300 mg/kg = 2.33% 27
Terra -  Manto:  16.6% 28
Terra -  litosfera:  2.76% 29
Terra -  Hidrosfera:  0.13% 29
Terra -  Total:  13.90% 30
Planeta Mercúrio) -  Total:  6.50% 30
Vênus -  Total:  14.54% 30
Universo -  Total:  0.06% 28
condritos - Total: 9.4×105 (relative to 106 atoms of Si) 31
Corpo humano - Total: 0.027% 32

compostos

preços





Informação de Segurança


Material Safety Data Sheet - ACI Alloys, Inc.

Para maiores informações

Links externos:

Fontes

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