chemist mohd irwan idris

8/13/2019 Chemist Mohd Irwan Idris

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SBCH 3203

ORGANOMETALLIC CHEMISTRY /KIMIA ORGANOLOGAM

SEPTEMBER 2011

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NAMA : MOHD IRWAN BIN IDRIS

MATRIK NO :810320145167001

NO. TEL :0166665247

EMAIL : eoneg e!"#$oo.%o&

'( : S$#$ A)#&
mailto:[email protected]:[email protected]


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*+ESTION 1

a) In the Electron - Sea model, the valence electrons of each atom are attracted to positively

charged nuclei of several close neighbours. As the result , the valence electrons become

free from attractives force of its o n nucleus. !he electrostatic force of attraction

bet een the positive ions and the sea of valence electrons is the metallic bond.

Sodium has the electronic structure "s ##s##p$%s". &hen sodium atoms come together, the

electron in the %s atomic orbital of one sodium atom shares space ith the corresponding

electron on a neighbouring atom to form a molecular orbital .

!he electrons can move freely ithin these molecular orbitals, and so each electron becomes detached from its parent atom. !he electrons are said to be delocalised . !his

cause the distance bet een the central metal cations ith the electron cloud farther, so

electrostatic attraction bet een the metal cations ith ea'er electrons cloud.


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(agnesium, end up ith stronger bonds and so a higher melting point. (agnesium has

the outer electronic structure %s#. oth of these electrons become delocalised, so the *sea*

has t ice the electron density as it does in sodium. !he remaining *ions* also have t ice

the charge and so there ill be more attraction bet een *ions* and *sea*.

(ore realistically, each magnesium atom has one more proton in the nucleus than a

sodium atom has, and so not only ill there be a greater number of delocalised electrons,

but there ill also be a greater attraction for them.

(agnesium atoms have a slightly smaller radius than sodium atoms, and so the

delocalised electrons are closer to the nuclei. Each magnesium atom also has t elve nearneighbours rather than sodium+s eight. oth of these factors increase the strength of the

bond still further. !his ill e plain hy the increasing boiling point from a to (g to Al

across the ro in a periodic table


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b) ifferent ligands have different effects on the energies of the d orbitals of the central ion.

Some ligands have strong field ligand hich cause a large energy gap hen the d orbitals

split into t o groups. !he si/e of gap determines the avelength of lights is going to getabsorbed. !he list belo sho s some common ligands ith the splitting

0 1 is a strong field ith the largest splitting need more energy to promote an

electron from the lo er group of orbitals to the higher ones. In terms of the colour of the

light absorbed, greater energy corresponds to shorter avelength, higher fre2uency. In

order to promote an electron, lue light has a higher energy ill be absorbed, to give the

complementary yello coloured.

!hose containing 3#4 is a ea' field ligand ill create a comple ith a smaller 5 ,

hich ill absorb light of longer 6 and thus lo er fre2uency, v. !he comple ith 3#4

ligands ill absorbed red light, in order to give the complementary green colour.

Cl smallest splitting

F

OH

H2O

NH3

CN largest splitting


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c) A covalent bond is formed by t o atoms sharing a pair of electrons. !he atoms are

held together because the electron pair is attracted by both of the nuclei. In the formation

of a simple covalent bond, each atom supplies one electron to the bond - but that doesn+t

have to be the case.

A coordinate bond 7also called a dative covalent bond) is a covalent bond 7a shared pair

of electrons) in hich both electrons come from the same atom.

Le,- A%-/ : a species that accepts an electron pair and ill

have vacant orbitals

E amples8 9 %, 3 : , 0u #: , 0r %:

Le,- B# e 8 a species that donates an electron pair and ill have lone-pair

electrons

E amples8 3 %, 43 -, 3 #4

!he reaction of a ;e is acid and a ;e is base ill produce a coordinate covalent bond,

as sho n in figure " belo . A coordinate covalent bond is


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A coordination comple is the product of a ;e is acid-base reaction in hich neutral molecules

7ligands) bond to a central metal atom by coordinate covalent bonds. 0ompounds that contain a

coordination comple are called coordination compound.

E ample8 T$e e#% -on e ,een #&&on-# #n/ $"/ ogen %$)o -/e

If these colourless gases are allo ed to mi , a thic' hite smo'e of solid ammonium chloride is

formed.

Ammonium ions, 3 =: , are formed by the transfer of a hydrogen ion from the hydrogen chloride

to the lone pair of electrons on the ammonia molecule.

&hen the ammonium ion, 3 =: , is formed, the fourth hydrogen is attached by a dative covalent

bond, because only the hydrogen+s nucleus is transferred from the chlorine to the nitrogen. !he

hydrogen+s electron is left behind on the chlorine to form a negative chloride ion.


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d) 3e aammine 0obalt 7III) chloride, > 0o7 3%)$?0l% in its octahedral geometry ith $

coordination number. !he central ion is 0o@: and three 0l ion as ionic bonds

iagram sho 8 BBBBBBBBBB .. ionic bonds

0ovalent bond

chemist mohd irwan idris

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