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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: Ashutosh on April 07, 2005, 06:08:08 AM

Title: molecular orbital theory
Post by: Ashutosh on April 07, 2005, 06:08:08 AM
I dont understand MOT.I know 1S orbital (first orbit) contain maximum 2 electrons.But I think sigma 1S & sigma*1s orbital are in the first orbit. Is it right ???according to this,electrons are filled in these orbital first.so,max.number of electron in 1 orbit is 4.is this not contractory with the second statement ???
 thanking you.
Title: Re:molecular orbital theory
Post by: AWK on April 07, 2005, 06:55:24 AM
Two electrons are either on 1s or 1s*
Title: Re:molecular orbital theory
Post by: Donaldson Tan on April 07, 2005, 08:15:20 PM
1s* exist?

i thought antibonding orbitals only exist for molecular orbitals, not atomic orbitals. antibonding orbitals arises when 2 atomic orbitals of -ve sign overlap with each other? how can there be such thing as 1s*?
Title: Re:molecular orbital theory
Post by: Ashutosh on April 08, 2005, 01:40:46 AM
Two electrons are either on 1s or 1s*

   according to MOT ,electrons are filled sequensially in 1S and then in 1S*.I think it is not possible to have electrons either on 1S or on 1S*.
             
                 another question
  when each two electrons filled in the 1s and 1S* then total number of electrons in the first orbit =4.how is it possible ???
Title: Re:molecular orbital theory
Post by: Mitch on April 08, 2005, 06:03:07 AM
Your confusing sigma orbitals with s orbitals.

MOLECULAR ORBITAL THEORY IS ONLY USED WITH BONDING: As such you will always have more then one atom present when you envoke MO theory.

A rule in MO Theory is that you need to have as many moleular orbitals as you have atomic orbitals. So, in the case of H2, where both hydrogens will donate their 1s orbital, for a total of two 1s orbitals. Correspondingly, two sigma orbitals need to be made as well the sigm bonding and the sigma antibonding.

Hope that helps.

Mitch
Title: Re:molecular orbital theory
Post by: Ashutosh on April 09, 2005, 04:54:43 AM
Thanks Mitch for helping.I get my difficulty cleared :)