Grade 12 AP Chemistry - Valence Bond Theory, Hybridization, M/NM/Metalloid Trends + Properties, Co-ordinate Covalent Bonding

Electron Domains/Steric #

total # of e- pairs (lone + bond pairs)

Electron Domain Geometry

lone pairs + bond pairs

e.g. AX₂E₂ e- domain geometry = tetrahedral

Molecular Geometry

only bond pairs

e.g. AX₂E₂ molecular geometry = bent

Bonding Domains

bond pairs

Non-Bonding Domains

lone pairs

Valence Bond Theory

model of bonding

bonding e- pairs are located between bonding atoms

non-bonding e-pairs are located in regions outside the bonding region

Valence bond theory only applies to what cpds?

covalent

Valence bond theory does not work well for ___________ atoms.

hypervalent (e.g. SF₆)

Draw the VBD for H₂

solution in notebook

Draw the VBD for HF

solution in notebook

σ bond/end-to-end overlap

bond between two nuclei where bonding e- line up along the internuclear axis

Internuclear Axis

horizontal line that goes through the nucleus

To be able to form a covalent bond, the atom has to be able to _____ and _______ an e-.

offer, receive

The first pair of e- to form a covalent bond is a _ bond. Therefore in covalent bonding, _ bonds are ALWAYS present.

σ, σ

Draw the VBD for F₂

solution in notebook

Hybridization

e- being promoted and subshells becoming degenerate

Degenerate Subshells

subshells that are equal in E (e.g. the 5 d subshells)

There are some atoms in cpds that don’t need to hybridize (bc they already have enough valence e-’s) but do. Why is this?

to allow for larger angles between the subshells and ∴ less repulsion ∴ a more stable molecule

When hybridization occurs, it is based on the __ ______ ________.

e- domain geometry

e.g. H₂O =

Co-ordinate Covalent Bonding

covalent bond in which both bonding e- come from the same atom

Co-ordinate Covalent Bonding is also called

DATIVE bonding

Hybridization vs Anomalous Configurations

Hybridization:

• ONLY happens when atom is bonding

• does NOT occur in isolated atoms

Anomalous:

• atom is ALWAYS anomalous; it does not “become” anomalous

a) Draw the VSEPR for methane, CH₄

b) Draw the VBD for methane, CH₄

solution in notebook

a) Draw the VBD for CH₂BrI

b) Identify i) the hybridization of the central atom and ii) the bond types

solution in notebook

e-’s in hybridized orbitals always form _ bonds

σ

unhybridized e- in the remaining parts of a multiple bond form _ bonds

π

Draw the VBD for CH₂CHBr

solution in notebook

Draw the VBD for CHCBr

solution in notebook

Except for _____ _____, no elements exist in nature as individual atoms. Only _____ _____ are monatomic.

noble gases, noble gases

Metals react with O₂ to form _____ oxides. _____ oxides form _____ solutions.

metal, metal, basic

Non-metals react with O₂ to form _________ oxides. _________ oxides form ______ solutions.

non-metal, non-metal, acidic

Hydrogen reacts with metals to form the _______ ion, H^-

hydride

Noble gases used to be considered “_____” (unable to react). However, under the right conditions, they can form cpds.

inert

_________ are strong oxidizers

peroxides

Oxide vs Peroxide vs Superoxide

Oxide: O^-2

Peroxide: O₂^-2

Superoxide: O₂^-

Allotrope

different forms of the same element in the same state (e.g. O₂ and O₃)

Why do NM tend to have high -ve E.A. values?

• E.A. is the E change when an e- is added to an atom

• if E.A. is -ve that means E is released (as atom becomes more stable)

• e- is added to p subshell which is one step closer to having a full valence shell

Give 3 examples of elements that form allotropes

O₂, O₃

As, As₄

P, P₄

Oxygen has a strong ability to oxidize other substances. What does this mean?

• having strong ability to oxidize other substances means u have a high EN and can ∴ attract their e-’s

Fluorine is one of the strongest oxidizers in the PT. It is also the smallest atom on the PT. How are these two facts related?

• F is a strong oxidizer, ∴ it has high EN, ∴ it has a small atomic radius bc it pulls on its e-’s a lot

Metal + water always produces __ gas on top of the base.

H₂

Draw the Lewis structure for NO₃^-

solution in notebook

Resonance (Hybrid) Structures

having more than one (right) structure for a molecule that just have different arrangements of their paired e-

NONE of these structures are the actual structure (the actual structure is a ‘hybrid’ of the resonance structures)

Draw the resonance structures for nitrate, NO₃^-

solution in notebook

a) Draw the resonance structures for i) O₃

b) Suggest a hybrid resonance

solution in notebook

a) Draw the resonance structures for ii)CO₃^-2

b) Suggest a hybrid resonance

solution in notebook

a) Draw the resonance structures for iii) SO₂

b) Suggest a hybrid resonance

solution in notebook

Formal Charges

NOT REAL CHARGES that help determine which structure of a molecule is the dominant one

There are resonance structures when the formal charges are exactly the ____ for all structures AND no one structure is clearly ________ above the others. (e.g. O³)

same, dominant (e.g. try drawing equivalent Lewis diagrams for SCN^- … they are NOT resonance structures because one is clearly dominant above the others)

How do you calculate formal charge?

(valence e-) - (e- assigned to the atom)

Calculate the formal charge of the structures of CO₂

solution in notebook

What do you do if multiple structures have the same formal charge?

the dominant structure is the one where the -ve charge is on the more EN atom

The dominant structure is the one whose atoms have a formal charge closest to _.

0

3 Exceptions to the Octet Rule

1. molecule/polyatomic ion has an odd # of e-

2. molecule/polyatomic ion has < 8 valence e-

3. molecule/polyatomic ion has > 8 valence e-

Hypervalence

expanded octet

due to forcing e-’s into the d orbital

Any molecule with steric #_ will hybridize.

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