major elements in the earth crust slide

8/3/2019 Major Elements in the Earth Crust Slide

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Atomic Number: 12

Atomic Weight: 24.3050

Melting Point:923 K (650C or 1202F) Boiling Point: 1363 K (1090C or 1994F)

Density: 1.74 grams per cubic centimeter

Phase at Room Temperature: Solid Element Classification: Metal

Period Number: 3 Group Number: 2

Group Name:Alkaline Earth Metal

12

Mg

Magnesium

24.3050


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PhysicalProperties

In solidphase

Fairlystrong

Mgcompoundtypically

white crystals

Meltingpoint:

650C, 923K,

1202F

BoilingPoint: 1363K,1091C, 1994F

Silverywhite

Light-weight

metal (twothirds thedensity of

aluminium)


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ChemicalProperties

Tarnished slightly

when exposed to air

React exothermically

with most acid such

as HCI

Produce thechloride of the

metal & release

hydrogen

Highly flammable

Being able to burn

nitrogen(forming magnesium

nitride), carbon dioxide (formingmagnesium oxide & carbon),&

water (forming magnesium oxide

& hydrogen)

Produce a briliant white light

while burning in air

Flame temperature of

magnesium & magnesium

alloys can reach 3100C

Soluble in water

Providing the sour-tasting

magnesium ion Mg2+Large amounts of

magnesium is an ionic

laxative


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Although magnesium is found in over 60 minerals, only dolomite, magnesite,brucite, carnallite, talc, and olivine are of commercial importance.

The Mg2+ cation is the second most abundant cation in seawater (occurring atabout 12% of the mass of sodium there), which makes seawater and sea-salt anattractive commercial source of Mg. To extract the magnesium, calcium hydroxide isadded to seawater to form magnesium hydroxide precipitate.

MgCl2 + Ca(OH)2

Mg(OH)2 + CaCl2Magnesium hydroxide (brucite) is insoluble in water so it can be filtered out,and reacted with hydrochloric acid to obtain concentrated magnesium chloride.

Mg(OH)2 +2HClMgCl2 + 2 H2OFrom magnesium chloride, electrolysis produces magnesium.

In the United States, magnesium is principally obtained by electrolysis of fusedmagnesium chloride from brines, wells, and sea water. At the cathode, the Mg2+ ionis reduced by two electrons to magnesium metal:

Mg2+ + 2 e MgAt the anode, each pair of Cl ions is oxidized to chlorine gas, releasing two

electrons to complete the circuit:

2 Cl

Cl2 ( g ) + 2 e


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As an additive agent inconventional propellants and

the production of nodulargraphite in cast iron

In the form of turnings orribbons, to prepare Grignardreagents, which are useful in

organic synthesis.

AS METAL

Alloyed with zinc to producethe zinc sheet used in

photoengraving plates in theprinting industry, dry-cellbattery walls and roofing.

As a sacrificial (galvanic) anode toprotect underground tanks,

pipelines, buried structures, andwater heaters.

As a reducing agent for theproduction of uranium andother metals from their salts


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Ascompound

Magnesiumhexafluorosilicate is used

inmothproofingof textiles.

Magnesium stearate is aslightly flammable whitepowder with lubricating

properties. In pharmaceutical

technology it is used in themanufacturing of tablets, toprevent the tablets from

sticking to the equipmentduring the tablet compressionprocess (i.e., when the tablet'ssubstance is pressed into tablet

form).

Magnesium carbonate(MgCO3) powder is also

used by athletes, such asgymnasts andweightlifters, to improve the

grip on objects theapparatus or lifting bar.

Dead-burnedmagnesite is

used forrefractory

purposes such asbrick and linersin furnaces and

converters

Magnesium borate,magnesium

salicylate andmagnesium sulfate

are used asantiseptics.

Magnesiumphosphate is

used tofireproof wood

forconstruction.

Magnesiumsulfite is used

in themanufacture

of paper(sulfite

process)


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major elements in the earth crust slide

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