Empty p-orbital in BF3?

[ball1313]

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Hi,

Can someone explain the logic behind the reason why BF3 (boron trifluoride) has an empty p-orbital and is a lewis acid? i dont understand how im just supposed to know that the p-orbital is 1) there and 2) empty

 

[JFK90787]

BF3 is sp2 hybridized, so I always imagine the s orbital and 2 of the p orbitals as all equal, I.E the s orbital and 2 of the p orbitals will have 1 electron each. 3 flurorines will bind to each of these 3 hybridized orbitals. This leaves one empty p orbital which can accept an electron pair.

If this isn't clear ask again, I always feel this is best explained with pictures

 

[unique135]

It's a concept of hybrid orbitals.

Boron's configuration state: 1s[2]...2s[2]...2px[1].2py[0].2pz[0]

Boron's configuration state in BF3: 1s[2]...sp2[1.1.1]...2pz[0]

sp2 orbitals reacts with fluoride atoms to form BF3 and there is empty p-orbital as well.

This empty p-orbital can be filled with coordinate covalent bonding. Example: BF3 + NH3 where NH3 donate its electron pair (thus basic) while BF3 accepts an electron pair (thus acidic).

 

[CaptainSSO]

I don't really think you would need to specifically know that BF3 is sp2 hybrized and has an empty P orbital for the MCAT. This information is a little too detailed.

Just know in general what hybridization and orbitals actually are.

As far as being a Lewis acid, if you're looking at a drawing or Lewis dot structure, you'll be able to tell that the compound BF3 doesn't have a lone pair. The 3 bonds with fluorine account for 6 electrons total, and thus it needs an additional electron pair in order to complete its octet.

Lewis acid = electron pair acceptor. Lewis base = electron pair donor. I remember these by just thinking of them as exactly opposite of Bronsted-Lowry acids and bases, the Bronsted acids being proton donors and Bronsted bases being proton acceptors, respectively. Protons and electrons have opposite charges, and acceptor/donor mean the opposite thing.

 

[Vanguard23]

Shouldn't it have a pi bond to be sp2 hybridized? I thought the three F's and lone electron pair make it sp3.

 

[ezsanche]

Shouldn't it have a pi bond to be sp2 hybridized? I thought the three F's and lone electron pair make it sp3.

Nope! two different yet interelated concepts.

 

[unique135]

Shouldn't it have a pi bond to be sp2 hybridized? I thought the three F's and lone electron pair make it sp3.

There is no lone pair here in BF3. BF3 is trigonal planar, not tetrahydronal as in sp3.

 

[Vanguard23]

There is no lone pair here in BF3. BF3 is trigonal planar, not tetrahydronal as in sp3.

Oi! I stand corrected.

 

[CaptainSSO]

There is no lone pair here in BF3. BF3 is trigonal planar, not tetrahydronal as in sp3.

tetrahedral?

 

[unique135]

tetrahedral?

lol, what was i thinking...yeah tetrahedral...