03.24.21 - Polar and Nonpolar Molecules
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Circle the picture that best describes how you are doing today.
Which celebrity or person important to you do you share your birthday with? Take a few seconds to google if you need to!
What is the shape of a molecule of OF2? Use the space below to draw a Lewis dot structure. Then use your dot structure and the VSEPR diagram to determine the shape of the molecule.
What is the shape of a molecule of SiO2? Use the space below to draw a Lewis dot structure. Then use your dot structure and the VSEPR diagram to determine the shape of the molecule.
Classify each bond as polar or nonpolar covalent using the electronegativity values given below.
Electronegativity Values
O = 3.5
F = 4.0
Si = 1.8
O - F
Si - O
polar covalent bond
nonpolar covalent bond
Objectives:
Students will:
use electronegativity values of elements to classify a covalent bond as nonpolar or polar.
indicate the direction of polarity in a polar covalent bond.
determine if a molecule is polar or nonpolar based on the molecule's three dimensional structure and electronegativity values of elements in the molecule.
Why?
The physical properties of a substance are dictated in part by whether or not a molecule is polar. For example, oil and water do not mix because water is polar whereas oil is nonpolar. Another example is carbon dioxide and water. At room temperature, carbon dioxide is a gas while water is a liquid because carbon dioxide is nonpolar while water is polar. In this activity, you will explore the factors that contribute to a molecule’s polarity or nonpolarity.
Use the diagram below to answer questions 6-19.
Match the picture to the type of bond.
| Stavka koja se može prevući | arrow_right_alt | Odgovarajuća stavka |
|---|---|---|
| arrow_right_alt | polar bond |
| arrow_right_alt | nonpolar bond |
Use your VSEPR chart to determine the molecule geometry for each molecule shown below.
linear
trigonal planar
bent
tetrahedral
trigonal pyramidal
Based on your answer to the previous questions, can the shape of a molecule explain polarity?
Nonpolar molecules _________ contain polar bonds.
Polar molecules _________ contain polar bonds.
A student states, “Polar molecules are just molecules that contain polar bonds. If there are no polar bonds, then the molecule is nonpolar.” Do you agree or disagree with this statement? Justify your reasoning using evidence from Model 1.
A pair of black dots on a molecule (see example below) represent _____.
Nonpolar molecules ________ contain lone pairs of electrons
Polar molecules ________ contain lone pairs of electrons
Is the presence or absence of a lone pair of electrons sufficient to explain the polarity of molecules?
When polar bonds are present in a nonpolar molecule, how are they arranged around the center atom—on the same side of the molecule or on opposite sides of the molecule?
When polar bonds are present in a polar molecule, how are they arranged around the center atom—on the same side of the molecule or on opposite sides of the molecule?
When lone pairs of electrons are present in a nonpolar molecule, how are they arranged around the center atom—on the same side of the molecule or on opposite sides of the molecule?
When lone pairs of electrons are present in a polar molecule, how are they arranged around the center atom—on the same side of the molecule or on opposite sides of the molecule?
Read This!
Polar molecules have an unequal distribution of charge around the molecule as a whole. This could be due to a bond being polar or a lone pair of electrons being present. Both would cause a concentration of negative charge on one side or in one area of the molecule due to an unequal distribution of electrons among nuclei. If a molecule has more than one polar bond or lone pair of electrons and they are symmetrically arranged, there is no unequal distribution of charge and the molecule is nonpolar.
Just remember this...
Symmetrical
Nonpolar
Asymmetrical
Polar
Revisit the warm-up questions about OF2 and SiO2. Look at the Lewis dot structures and the bond polarities.
Classify these molecules as either polar or nonpolar.
OF2
SiO2
polar molecule
nonpolar molecule
Practice time!
Now it's your time to practice determining if a molecule is polar or nonpolar. To do this, complete the following steps:
Draw the Lewis dot structure of the molecule
Determine if the bonds in the molecule are polar or nonpolar using the electronegativity chart below.
Draw the three dimensional shape of the molecule (VSEPR model).
Determine if the molecule is polar or nonpolar.
You must complete 2 questions below. For example, you could complete questions 21 and 22 or questions 22 and 23. The questions get more difficult as you go, so start with Level 1 and see if you can get to harder questions in Level 3!
If you're still feeling stuck on how to predict whether a molecule is polar or nonpolar, check out the video below.
Electronegativity Values of Elements
Complete the table below. These questions are Level 1 questions.
Complete the table below. These questions are Level 2 questions.
Complete the table below. These questions are Level 3 questions.
