[GOPgabe]

Hey guys, I was faced with a problem recently that I got wrong    An explanation would be much appreciated.

Choose the statement that INCORRECTLY completes the statement: A molecular orbital _____.

a) is never occupied by more than one electron
b) can be formed from the overlap of two p_x orbitals
c) exists in some polyatomic species
d) is a combination of atomic orbitals on different atoms
e) can be either lower or higher in energy than the two orbitals from which it is formed.
 
According to my answer key, the answer is C.
I thought it was A due to electrons having to fill up both bonding and anti-bonding orbitals with opposite spins, so I clearly need to do my research! An explanation of each answer would be favorable. Thanks.

[Jorriss]

Choose the statement that INCORRECTLY completes the statement: A molecular orbital _____.

a) is never occupied by more than one electron
b) can be formed from the overlap of two p_x orbitals
c) exists in some polyatomic species
d) is a combination of atomic orbitals on different atoms
e) can be either lower or higher in energy than the two orbitals from which it is formed.

A Molecular Orbital - like every orbital - can be occupied by upto two electrons, eliminating A right off the bat.

Molecular orbitals are formed by overlap of atomic orbitals - eliminating b and d.

There are lots of MO's  - antibonding and bonding MO's being the key to e. Antibonding orbitals can have higher energy than the individual atomic orbitals, eliminating e.


MO orbitals exist in EVERY molecule, therefore every polyatomic species has MO's, not just some. C is the right answer.

[GOPgabe]

I just realized I read the question wrong. That "some" was sneaky!    Thanks man!

Oh, but wait isn't A Incorrect also if it can be occupied by more than one? It says can NEVER be occupied by more than one. 2 electrons is possibility.

[Jorriss]

Yeah, the 'incorrect' part is throwing me off (ive read it like ten times), I think A is right too now that you mention it.