2.2.3 Polar Covalent Bonds, Hydrogen Bonds, and Van der Waals Interactions

Question 1

polar covalent bonds

Answer 1

• when one atom in a covalent bond is more electronegative than the other.
• covalent bonds that do not have their electrons shared equally between atoms. One atom may have a higher
  electronegativity than the other atom in the bond.

Question 2

hydrogen bonds

Answer 2

• form from interactions between a partially positive hydrogen in one molecule and a partially negative atom (usually oxygen or nitrogen) in another molecule.
• weak bonds resulting from the attraction of the partially positive hydrogen on one molecule and the partially negative atom (usually oxygen or nitrogen) on
  another molecule.
• DNA is made of two nucleic-acid strands that are hydrogen-bonded together

Question 3

Van der Waals interactions

Answer 3

• weak interactions between regions of nonpolar

molecules, resulting from charge fluctuations within molecules.

Question 4

note

Answer 4

• In the case of water, at moments the oxygen can take the electron from hydrogen. Sometimes hydrogen will get it back. Because oxygen has the higher electronegativity, it can take the electron more often, generating a partially negative charge on the oxygen and a partially positive charge on the hydrogen.

Question 5

Long hydrocarbon chains such as oils are attracted to one another because of

Answer 5

• van der Waals interactions

Question 6

Can hydrogen bonds occur between water molecules?

Answer 6

• yes because there are partially positive hydrogen atoms and partially negative oxygen atoms

Question 7

Oxygen is much more electronegative than hydrogen. Which of the following statements about the OH group in methanol (CH3OH) is true?

Answer 7

• The hydrogen atom has a partial positive charge.

Question 8

The oxygen atom in an H2O molecule

Answer 8

• carries a partial negative charge

Question 9

The partial negative charge on the oxygen of a methanol molecule (CH3OH) is attracted to the partial positive charge of another methanol molecule. This attraction is called

Answer 9

• a hydrogen bond

Question 10

Which type of bond has unequally shared electrons?

Answer 10

• polar covalent

Question 11

Which of the following pairings would result in a polar covalent bond?

Answer 11

• carbon and oxygen

Question 12

Hydrogen bonding occurs between molecules in which hydrogen atoms are bound to small, highly electronegative atoms. Which of the following groups of atoms are most likely to result in hydrogen bonding when paired with hydrogen?

Answer 12

• nitrogen, oxygen, fluorine

Question 13

Hydrogen bonds can provide strength to large molecules because

Answer 13

• large molecules may have multiple sites where hydrogen bonding can occur.

Question 14

Which of the following chemical bonds is the weakest?

Answer 14

• van der Waals