Humboldt State University ® Department of Chemistry

Richard A. Paselk

	General Chemistry	Spring 2015
Exercise: Hybrid Molecular Orbitals	© R. Paselk 2015
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Hybrid Molecular Orbitals

Determine the hybrid molecular orbital type, molecular shapes, bond type(s) and polarities for the covalent molecules below. You may want to make Lewis Structures first in order to determine the steric numbers for each molecule. A Periodic Table is provided with Hi (red), Lo (gray) and Intermediate (green) Electronegativities indicated to aid in predicting polarity.

Example: Formaldehyde, CH₂O

• LS =
• SN = 3, therefore hybridization = sp², no lone pairs so molecular shape = hybrid orbital shape = trigonal planar
• three sigma (single) bonds, one pi (double) bond;
• Polarity: C and O have significantly different Electronegativity values (2.5 & 3.5), so the C-O bond will be polar, with O partially negative. C and H differ only slightly in EN (2.5 & 2.1), so the C-H bonds will be only slightly polar.

• Formaldehyde is polar as shown with the dipole arrow:

Periodic Table of the Elements

IA

IIA

IIIA

IVA

VA

VIA

VIIA

VIIIA

H

He

2

Li

Be

B

C

N

O

F

Ne

3

Na

Mg

IIIB

IVB

VB

VI

VIIB

VIIIB

IB

IIB

Al

Si

P

S

Cl

Ar

4

K

Ca

Sc

Ti

V

Cr

Mn

Fe

Co

Ni

Cu

Zn

Ga

Ge

As

Se

Br

Kr

5

Rb

Sr

Y

Zr

Nb

Mo

Tc

Ru

Rh

Pd

Ag

Cd

In

Sn

Sb

Te

I

Xe

6

Cs

Ba

Lu

Hf

Ta

W

Re

Os

Ir

Pt

Au

Hg

Tl

Pb

Bi

Po

At

Rn

1. Methane, CH₄

2. Hydrogen sulfide

3. Carbon monoxide

4. Ammonia, NH₃

Set A - Answers 1-4

1. Formaldehyde, CH₂O

2. Carbon dioxide, CO₂

3. Chloromethane, CH₃Cl

4. Acetic acid, CH₃CO₂H

5. Ozone, O₃

6. Sulfite ion

7. Water, H₂O

8. Carbocation, CH₃⁺

Set B - Answers 1-8

1. Phosphorus pentachloride, PCl₅.

2. Sulfur tetrafluoride, SF₄.

3. Arsenic hexafluoride ion, AsF₆^-.

4. Iodine pentachloride, ICl₅.

Set C - Answers 1-4

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In addition to these exercises you should familiarize yourself with the text materials.

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Go to Report to get credit for Module

© R A Paselk

Last modified 20 April 2015