Ch 9 Part 3-5

Question 1

What are the two quantum mechanical theories that describe covalent bond formation?

Answer 1

Valence Bond Theory (VB) - assumes electrons occupy atomic orbitals of individual atoms; individual atoms participate in forming bonds (Unit 3)

Molecular Orbital (MO) Theory -atomic orbitals form molecular orbitals (Unit 4)

(Atomic Orbitals are 1s, 2p, 3d, 4f, etc)

Question 2

The mixing of atomic orbitals to form hybrid orbitals is called?

Answer 2

Hybridization

(Take a 1s and a 2p and mix them together to form a different combined hybrid orbital)

Question 3

Atomic orbitals obtained when two or more non-equivalent orbitals (a 2s & 2p mixed together) of the same atom combine for covalent bonding they form what?

Answer 3

Hybrid Orbitals

Question 4

How do we move electrons From
1 level to another in hybridization? Like 2s to 2p?

Answer 4

We energetically excite the electron to the next higher level

This separates electrons into all paramagnetic orbitals open for the maximum # of bonds with electrons from other atoms

Question 5

The # of atomic orbitals used will always be

Answer 5

The # of atomic orbitals formed, these numbers are ALWAYS THE SAME #!

Question 6

BF3 Lewis structure and hybridization

Answer 6

::F: :F::
\ /
B [H] 2s2,2p1 becomes 2s1,2p2
| sp2 hybridization
:F:: These creates the 3 unpaired
Electrons the F bonds to
3 atomic orbitals/3hybrid orbitals used

Question 7

1) When given SF6, what do we do first?
2) for hybridization we look at?

Answer 7

1) Draw the Lewis structure
2) central atom orbitals
3) we should get 6 unpaired electrons to create 6 bonds to the Fs
4) we move all paired electrons over giving us all unpaired electrons for bonds

Question 8

Phosphorus PentaBromide
Lewis Structure and Hybridization

Answer 8

5 atomic orbitals used, 5 hybrid orbitals formed, sp3d hybridization

Question 9

5 types of hybridization that exists :

Answer 9

Sp, sp2, sp3, sp3d, sp3d2

And only these 5 exist

Question 10

SbF5 orbital diagram

Answer 10

Question 11

NH3 hybridization with lone pair electrons

Answer 11

The lone pair is represented by a pair of electrons that are already paired

Question 12

Is there such a thing as no hybridization?

Answer 12

No, everything has hybridization

Question 13

Steps involved in hybridization

Answer 13

1) draw the Lewis structure
2) write out orbital diagram of the outer shell of the central atom(noble gasshrtct)
3) determine how many bonds must be made to the central atom
4) promote electrons to the next higher level within the shell
5) count the # of orbitals involved in hybridization

Question 14

Hybridization when molecules have double/triple bonds

Answer 14

Atomic Hybridization with double and triple bonds

If central atom forms a double bond sp2

It the central atom forms a triple bond sp

Question 15

Covalent bonds formed by orbitals, overlapping, end-to-end are called

Answer 15

Sigma bonds = single bonds

Question 16

Covalent bonds formed by sideways overlapping of orbitals above and below the plane of bonding atoms

Answer 16

Pi bonds

Question 17

Double bond consists of

Answer 17

1 sigma bond, 1 pi bond

Question 18

Triple bond consists of

Answer 18

1 sigma, 2 pi bonds

Question 19

Bonds in C6N4

Answer 19

Question 20

Answer 20

B 6 sigma 3 pi bonds

Question 21

Helium exists as

Answer 21

Isolated atoms with a bond order of 0
-it creates no bonds

Question 22

F2 is a

Answer 22

Molecule with a single bond

Bc it has 6 electrons in bonding molecular orbitals and 4 electrons in antibonding = 2 divided by 2 = 1 bond

Question 23

N2 nitrogen gas

Answer 23

Almost completely inert bc it has a triple bond -diatomic molecule with triple bond

Bond order is 6-0/2= 3 - triple bond

Question 24

02

Answer 24

Diatomic molecule with 1 double bond

Bond order (6-2)/2=2 =double bond

Question 25

When all electrons are paired this molecule is ____? Which means? _____

Answer 25

When all electrons are paired, the molecule is diamagnetic which means repelled by a magnet

Question 26

Discrepancy in Valence Bond Theory

Answer 26

O2 - all electrons are paired so it should be diamagnetic (repelled by a magnet) , but experiment show is paramagnetic (attracted to a magnet).

Question 27

Bonding molecular orbitals have _____ energy and _______ stability The atomic orbitals formed from it.

Answer 27

Bonding molecular orbitals have lower energy and greater stability than the atomic orbitals formed from it

Question 28

Anti-bonding molecular orbitals have _____ energy and _______ ability then the atomic orbitals formed from it

Answer 28

Anti-bonding molecular orbitals have higher energy and lower stability than the atomic orbitals formed from it

Question 29

When electrons are left unpaired, this molecule would be considered ________? This means that it is _________?

Answer 29

When electrons are left unpaired, this molecule would be considered PARAMAGNETIC. This means that it is ATTRACTED TO A MAGNET.

Question 30

Is O2 paramagnetic or diamagnetic? Is it attracted to or repelled by a magnet?

Answer 30

O2 is an exception to the rule. All electrons are paired, however it is attracted to a magnet, making it paramagnetic.

Question 31

How is Bond order calculated?

Answer 31

1/2 (bonding molecular orbitals — anti-bonding orbitals) Anti-bonding orbitals are higher up with a * next to them When you total a WHOLE #, the molecule is STABLE

Question 32

H2 paramagnetic or diamagnetic?

Answer 32

Paramagnetic

Question 33

H2 +1 has how many electrons?

Answer 33

Each H should have 1 electron, however the +1 charge means we lost an electron, therefore H2+1 only has 1 total electron so we would show only 1 electron under the left H and 1 electron in the combined molecule of both H’s in the center. No electron under the H on the right side

Question 34

A bond order or 1/2 suggests that the molecule?

Answer 34

May be stable or may not be stable, further tests are needed

Question 35

Bond length

Answer 35

More e-, stronger bond but shorter Less e-, weaker bond but longer length Pertains ONLY to BONDING ORBITALS in the center MOLECULE (no star orbitals)

Question 36

Localized means? Delocalized means?

Answer 36

Localized means “stuck in position” (local) DeLocalized means “free to move around”

Question 37

Resonance structures for ?

Answer 37

Benzene Carbons always have 4 bonds and usually 1 of the 4 is to a Hydrogen

Question 38

How do you represent a Delocalized system where electrons are free to move around the ring?

Answer 38

The hexagon with circle in the middle is used rather than the 2 resonance structures shown above it in the picture below.