Mo baru.docx

8/18/2019 Mo baru.docx

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MOLYBDENUM

HISTORY

Molybdenum was discovered by

Molybdenum was discovered by Carl

Welhelm Scheele, a Swedish chemist, in

1778 in a mineral known as molybdenite

(MoS2) which had been conused as a lead

com!ound" Molybdenum was isolated by

#eter $acob %&elm in 1781" 'oday, most

molybdenum is obtained rom molybdenite,

wulenite (#bMo) and !owellite

(CaMo)" Molybdate are *uite rare

NATURAL ABUNDANCE

Molybdenum occurs as the mineral molybdenite MoS2" World !roduction o ores in 1+88 had

a molybdenum content o +2 tonnes" 'he lar-est source are

1" .S/ 70

2" Chile 1" 0

" Canada 1" 0

" .SS3 12" 0

Some MoS2 is also obtained as a by4!roduct rom CuS ores" Some molybdenum is obtained

as a by4!roduct o tun-sten and co!!er !roduction" World !roduction is around 2,

tonnes !er year"

PHYSICAL PROPERTIES

#hase 5 Solid

Meltin- #oint 5 262C

oilin- #oint 5 6C


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9ensity 5 1"28 -:cm

%eat o usion 5 7"8 k$:mol

%eat o ;a!orilectrone-ativity accordin- to #aulin- 5

1"8

;anderwaals radius 5 "1+ nm

?onic radius 5 "6+ Å (@),

"68 nm (@), "6 nm (@8)

Covalent radius 5 1A !m

?soto!s 5 11

>lectronic Shell 5 B=r d s1

?oniner-y 5 1st 68 k$:mol

2nd 16 k&:mol

rd 2618 k$:mol

Standard #otential 5 4"2 ;


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EXTRACTION'hou-h molybdenum is ound in such minerals as wulenite (#bMo) and !owellite

(CaMo), the main commercial source is molybdenite (MoS2)" Molybdenum is mined as a

!rinci!al ore and is also recovered as a by!roduct o co!!er and tun-sten minin-"

?n molybdenite !rocessin-, the ore is irst roasted in air at a tem!erature o 7 C (1,2+2 D)"

'he !rocess -ives -aseous sulur doEide and the molybdenum (;?) oEide5

2 MoS2 @ 7 2 F 2 Mo @ S2

'he oEidi


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-ive erromolybdenum, which is then added to steel" #ure Mo is obtained by dissolvin-

Mo dilute in G%% and !reci!itatin- ammonium molybdate, dimolybdate or !ure

molybdate" 'his is reduced with hydro-en to -ive metal" Mo metal is used as a catalyst in the

!etrochemical industry"

OXIDES STATES

OXIDATION STATES AND ISOTOPES

Common oxidation states 6,,,,2,

Isotopes ?soto!es /tomic Mass Gatural /bundance (0) %al Hie Mode o 9ecay+2

Mo +1"+7 1"77 I E 117

y β @4>C+Mo +"+ +"2 4 4+Mo +"+6 1"+ 4 4+6Mo +"+ 16"68 4 4+7Mo +6"+6 +"6 4 4+8Mo +7"+ 2"1+ 4 41Mo ++"+7 +"67 6 E 12 y β− β−¿

USES and APPLICATION

BIOLOGICAL ROLE

Nito!enases

'he most im!ortant role o the molybdenum in livin- or-anisms is as a metal

heteroatom at the active site in certain en


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'he reaction that nitro-enase en


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molybdate" Molybdenum en


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&oint !ains in the knees, hands, eet, articular deormities, erythema, and edema o the &oint

areas"

EN+IROMENTAL E,,ECT o& MOLYBDENUM

Molybdenum is essential to all s!ecies" /s with other trace metals, thou-h, what is essential

in tiny amounts can be hi-hly toEic at lar-er doses" /nimal eE!eriment have shown that too

much molybdenum causes etal deormities" Dodder with more than 1 !!m o molybdenum

would !ut most livestok at risk"

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Mo baru.docx