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Sidwick Theory
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Explains the electronic structure of complex, EAN rule, stability of complexes, defects

Budumuru Pushpalatha
M.Sc.,B.Ed., SET qualified; 11+ years of teaching experience, Reading books, listening music, Gardening

Unacademy user
sir .or lessons bnaye plzz......and in lessons best mcqs lesson bhi bna dijiye
Kapil Kumar
2 years ago
Yeah.. I ll do surely.. Thank you :)
explanation is too good
It was an good explanation and it was easy to understand the theory better.
Got clarity on sidwick theory .thanks
I liked ur way presentation keep it up

  2. About Me M.Sc; B.Ed 3 Years of Industrial Experience 11+ Years of Teaching Experience Reading Books, Listening Music,Gardening Rate Review Recommend and Share

  3. Sidwick theory: This theory developed the electronic structure of elements Werner's primary valencies were regarded as formed by electron transfer. .Secondary valencies were regarded as formed by electron pair sharing. All molecules which coordinate to metal ions have atoms with at least one unshared electron pair in their structure

  4. Those electrons are donated to central metal in the formation of the bond. * The atom giving the electrons is called Donor. The metal accepting it is called the Acceptor. Werner's secondary valencies are special form of covalent bonds termed as coordinate bonds. Such bonds are always indicated by an arrow.

  5. Head represents the acceptor atom. Tail represents the donor atom. Thus the structure of the complex is represented as below: 3 NHa

  6. EAN Rule . This rule tells the stability of the complex. The total number of electrons in the metal ion and those donated by ligands is equal to that of next higher noble gas . This total number of electrons is called EAN of the metal For ex: [Co(NH) Atomic number of cobalt-27 Co is present in the oxidation state +3 Total number of electrons in Co3+ 27-3 24

  7. Each NH3 gives 2 electrons to cobalt ion 6 NH2 ligands gives 6x2- 12 electrons 3+ The EAN of Co5 in the complex- 24+12-36 36 is the atomic number of krypton EAN rule is valid on this complex. * This complex will be stable

  8. For ex: [Fe(CN)J Atomic number of Iron-26 . Fe is present in the oxidation state= +3 . Total number of electrons in Fe - 26-3 23 Each CN gives 2 electrons to Iron ion 6 CN ligands gives 6x2- 12 electrons The EAN of Fe in the complex 23+12-35 . 35 is not the atomic number of noble gas. EAN Rule is not valid on this complex. This complex is unstable

  9. Defects . Does not predict the type of metal orbitals which may be involved in bonding. complexes exhibit more than one coordination number. . Does not predict the magnetic behaviour of . Does not explain why certain metal ions