Electronegativity and Lewis Structure Review Notes

By Christopher Powers

​Electronegativity and Lewis Structure Review Notes

Essential Questions

• How is electronegativity used to determine bond type?

• How do polar and nonpolar covalent bonds and polar and nonpolar
molecules compare and contrast?

• What are the characteristics of covalently bonded compounds?

Electronegativity and Polarity
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Electronegativity and Bond Character

• Electron affinity measures the tendency of an atom to accept an electron.

• Noble gases are not listed because they generally do not form compounds.

Electronegativity and Polarity
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• The relative ability of an atom to attract electrons in a chemical bond is called
electronegativity.

Multiple Choice

Partial charges are present in which type of bond?

• Ionic

• Nonpolar Covalent

• Polar Covalent

• Both Polar Covalent and Ionic

Electronegativity and Bond Character

• This table lists the character and type of chemical bond that forms with
differences in electronegativity.

Electronegativity and Polarity
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Electronegativity and Bond Character

• Unequal sharing of electrons results in a polar covalent bond.

• Bonding is often not clearly ionic or covalent.

• This graph summarizes the range of chemical bonds between two atoms.

Electronegativity and Polarity
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•​ The polarity of a bond is determined by the difference in the electronegativities of the two atoms.

Multiple Choice

Unequal sharing of electrons results in which of the following?

• polar covalent bond

• non polar covalent bond

• ionic bond

Multiple Choice

Order the types of bonds based on the charge of their molecules. (lowest amount of charge to greatest)

• Polar Covalent --> Ionic --> Nonpolar Covalent

• Ionic --> Nonpolar Covalent --> Polar Covalent

• Ionic --> Polar Covalent --> Nonpolar Covalent

• Nonpolar Covalent --> Polar Covalent --> Ionic

Polar Covalent Bonds

• Polar covalent bonds form when atoms pull on electrons in a molecule unequally.

• Electrons spend more time around one atom than another resulting in partial
charges at the ends of the bond called a dipole.

Electronegativity and Polarity
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​• In a polar covalent bond, the electrons gather around the atom with the Greatest Electronegativity.

Multiple Choice

The polarity of a bond is determined by...

• The sum of the electronegativities of the two atoms

• The difference in the electronegativities of the two atoms

• The charges of the atoms

• None of the Above

Multiple Choice

In a polar covalent bond, the electrons gather around...

• The atom with the Greatest Electronegativity

• The atom with the Lowest Electronegativity

• Each atom Equally

• None of the Above

Polar Covalent Bonds

• Covalently bonded molecules are either polar or non-polar.

• Non-polar molecules are not attracted by an electric field.

• Polar molecules align with an electric field.

• Compare water, H2O, and CCl4.

–Both bonds are polar.

–The molecular shapes, determined by VSEPR, is bent and tetrahedral, respectively.

–O – H bonds are asymmetric in water, so has a definite positive end and
definite negative end. Thus, polar. The C – Cl bonds are symmetrical in CCl4.
The electric charge measured at any distance from the center is identical on all sides and partial charges are balanced. Thus nonpolar.

Electronegativity and Polarity
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Polar Covalent Bonds

• Note: If bonds are polar, asymmetrical molecules are polar and symmetrical molecules are nonpolar.

Electronegativity and Polarity
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Multiple Choice

True or False: If bonds are polar, asymmetrical molecules are polar and symmetrical molecules are nonpolar.

• True

• False

Polar Covalent Bonds

• Solubility is the property of a substance’s ability to dissolve in another substance.

• Polar molecules and ionic substances are usually soluble in polar substances.

• Non-polar molecules dissolve only in non-polar substances.

Electronegativity and Polarity
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Properties of Covalent Compounds

• Covalent bonds between atoms are strong, but attraction forces between
molecules are weak.

• The weak attraction forces are known as van der Waals forces.

• The forces vary in strength but are weaker than the bonds in a molecule or
ions in an ionic compound.

• Non-polar molecules exhibit a weak dispersion force, or induced dipole.

• The force between two oppositely charged ends of two polar molecules is a dipole-dipole force.

• A hydrogen bond is an especially strong dipole-dipole force between a
hydrogen end of one dipole and a fluorine, oxygen, or nitrogen atom on
another dipole.

Electronegativity and Polarity
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Multiple Choice

What type of molecules exhibit a weak dispersion force, or induced dipole?

• Polar

• Non-polar

• Ionic

Properties of Covalent Compounds

• Many physical properties are due to intermolecular forces.

• Weak forces result in the relatively low melting and boiling points of
molecular substances.

• Many covalent molecules are relatively soft solids.

• Molecules can align in a crystal lattice, similar to ionic solids but with less
attraction between particles.

• Solids composed of only atoms interconnected by a network of covalent
bonds are called covalent network solids.

• Quartz and diamonds are two common examples of network solids.

Electronegativity and Polarity
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Lewis Dot Structure Review

What are Lewis Dot Structures? What can they tell us?

• How many BONDS an atom can make

• How many VALENCE ELECTRONS an atom has

Multiple Choice

Recap: What are Valence Electrons?

• Inner most electrons

• Outer most electrons

• Electrons that only form bonds

Valence Electrons

• Are the outer most electrons of an atom

• They are usually represented by what group an atom is in

Groups

Groups go UP AND DOWN. There are 18 groups total on the periodic table. Groups have names known as families

What do group numbers tell us?

Each group number tells us the number of valence electrons, which tell us the Lewis Dot Structure of an atom

Multiple Choice

You can use the _______ to tell you information about the atom's Lewis Dot Structure

• Group number

• Period number

• Name

Multiple Choice

Using this picture, which group do these atoms belong to?

• Group 2

• Group 12

• Group 10

• Group 8

Multiple Choice

Which structure belongs to group 14?