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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: cliverlong on January 05, 2009, 04:28:20 PM

Title: Dative bonding in hydrated magnesium
Post by: cliverlong on January 05, 2009, 04:28:20 PM
Hi,

  I saw another exam question the answer to which I don't understand. The question was (among other things)

“what is the bonding between oxygen and magnesium in hydrate magnesium ion [Mg(H2O)6]2+?”

I wrote ligand but the provide answer is dative covalent.

I understand oxygen can provide (two) lone pairs of electrons. However, Magnesium is Group 2, period 3.

The order of energy levels is : 3s, 3p, 4s, 3d, with a big jump between 3p and 4s with a further jump to 3d.

Can the oxygen lone pairs (one pair from each of the six oxygens) form dative covalent bonds into the 3d orbital?

Thanks

Clive

Title: Re: Dative bonding in hydrated magnesium
Post by: Astrokel on January 06, 2009, 12:17:41 AM
I think it is possible but i am not very sure ;D
Title: Re: Dative bonding in hydrated magnesium
Post by: Vidya on January 06, 2009, 02:11:58 AM
Hi
when ligands approach Mg 2+ ion, energy of empty  orbitals changes and becomes suitable to accept electrons from ligands.That can be the reason that sp3 hybrid orbitals of oxygen atom in water molecule can form dative bonding with  empty orbitals of Mg2+
Title: Re: Dative bonding in hydrated magnesium
Post by: cliverlong on January 06, 2009, 09:59:59 AM
Quote from: vidya kaushik on January 06, 2009, 02:11:58 AM
Hi
when ligands approach Mg 2+ ion, energy of empty  orbitals changes
can you please provide a reference for that so I can read up on the effect?
Quote
and becomes suitable to accept electrons from ligands.That can be the reason
can be or is? Do you know?
Quote
that sp3 hybrid orbitals of oxygen atom in water molecule can form dative bonding with  empty orbitals of Mg2+
OK, that is what I am guessing but can you identify which orbitals in Mg2+ are occupied by oxygen lone pair? 3d orbital as I am guessing?


Thanks

Clive