 Intermolecular forces, in addition to being caused by bonding, actually exist within the bonds.
 Only polar species are involved in intermolecular forces.
 Hydrogen bonds are actual bonds within a molecule, as opposed to intermolecular forces between the
separate molecules.
Targeted Responses
1. What is represented inside each box in Model 1? Water molecules.
2. In relation to the box for molecule 1, where do the intramolecular forces exist? Inside the box.
3. Based on the intramolecular forces for molecule 1, draw similar asterisks for the intramolecular forces on the
diagram for molecules 2 and 3. (Asterisks drawn on rest of the covalent bonds.)
4. In relation to the molecule, where do intramolecular forces tend to occur? Within the molecule.
5. Two intermolecular forces exist in Model 1. Where are they positioned relative to the molecules? They are
between the molecules.
6. State, in everyday language, the difference between intermolecular and intramolecular forces in terms of where
they occur on the molecular level. Intramolecular forces occur within/inside molecules, while
intermolecular forces occur between molecules.
7. The diagram above represents an arrangement of five molecules. What is the difference between the two ends
of each molecule? One side is positively charged; the other side is negatively charged.
8. Molecules with the property you identified in #7 are known as dipoles. Consult with your group and reach a
consensus on what you think a dipole is. Write down this definition. A dipole is a species with one positively
charged end and one negatively charged end.
9. Consider the attractive forces shown in Model 2. In terms of the positive and negative ends of the dipoles,
where do attractive forces occur? Attractive forces occur between one positive and one negative end.
10. Consider the repulsive forces shown in Model 2. In terms of the positive and negative ends of the dipoles,
where do repulsive forces occur? Repulsive forces occur between two positive ends or between two
negative ends.
11. The forces described in #9 and #10 are called dipole-dipole interactions. How might dipole-dipole
interactions help many molecules attract each other? Dipoles are held together by the attraction between
the oppositely charged ends of the separate molecules for each other.
12. What causes the dipole in polar covalent molecules? Uneven sharing of electrons.
13. How are the partial charges represented for polar covalent molecules? δ- and δ+
14. In the diagram below, a hydrogen iodide molecule has been drawn with its partial positive and partial negative
charges. Using the three molecules in the box, draw an attractive force between two HI molecules using a
dashed line (- - -) and a repulsive force between two HI molecules using a dotted line (.....). Repulsive forces
should be shown between two ends of the same partial charge. Attractive forces should be drawn
between two ends of opposite charge. Answers may vary.
©HSPI – The POGIL Project Limited Use by Permission Only – Not for Distribution
Intermolecular Forces C1YvM
9
15. Nonpolar molecules do not form dipoles, because electrons are shared evenly. Would you expect nonpolar
molecules to “stick together” more or less effectively than polar molecules? Explain your answer in terms of
dipole-dipole interactions. Nonpolar molecules would “stick together” less effectively than polar
molecules, because they lack the dipole that would enable them to form positive and negative ends
that hold together with dipole-dipole interactions.
16. Below is a diagram of ammonia. Draw two more ammonia molecules in the box, indicating the partial positive
and partial negative charges for each molecule. Look for the completed molecules, including the partial
charges.
17. Draw the attractive forces between the ammonia molecules with a dotted line. Label these forces hydrogen
bonds. The students should label the attractive forces between oppositely charged ends of two
different ammonia molecules. They should not label bonds within the molecules themselves.
18. Indicate and label one covalent bond in the box. Students should label a covalent bond within one of the
molecules.
19. Is a hydrogen bond the same as a covalent bond? No.
20. With your group, explain your answer to #20, including:
a. how a covalent bond is formed. A covalent bond is formed by the sharing of electrons
between two atoms.
b. how a hydrogen bond is formed. A hydrogen bond is formed by the dipole-dipole interactions
between two polar molecules containing hydrogen bonded to nitrogen, oxygen, or fluorine.
c.
how the two are similar or different. Hydrogen bonding is an intermolecular force that results
from uneven electron sharing within the molecule. Covalent bonding is the sharing of the
electrons themselves and happens within the molecule. Hydrogen bonding is
intermolecular, and covalent bonding is intramolecular.
21. Bob’s sheep like to wander around the pasture. They could be found anywhere at any moment. How are Bob’s
sheep distributed in box A? They are distributed evenly throughout the pasture.
22. How are Bob’s sheep distributed in box C? Are the woolly sheep even across the pasture? No, the woolly
sheep are not distributed evenly throughout the pasture.
23. Looking at the sheep in box C, identify a ‘woolly’ area and a ‘non-woolly’ area. Label the woolly area W and the
non-woolly area NW. The bottom left corner of the square should be labeled with a W. The top right
corner of the square should be labeled with an NW.
24. Now let’s look at the krypton atoms in boxes B and D.. Electrons, like sheep, like to wander around the atom.
How many protons and electrons are in the atom in these two boxes? There are 18 protons and 18 electrons
in each atom.
25. Is each atom electrically neutral? Explain. The atoms in each row are neutral, because they have an equal
number of protons and electrons.
26. In box B, are the electrons evenly distributed around the nucleus? Explain
evenly, and no area has too many or too few electrons.
The electrons are distributed
©HSPI – The POGIL Project Limited Use by Permission Only – Not for Distribution
Intermolecular Forces C1YvM
10
27. In box D, are the electrons evenly distributed around the nucleus? Explain. The electrons are distributed
unevenly in the bottom row.
28. In box D, indicate any area that is crowded with electrons with a “δ-“, and any area where the nucleus is
exposed with a “δ+.”The left side of the square should be labeled partially negative, while the right
side should be labeled partially positive.
29. Even though the krypton atom in #29 is electrically neutral, why could it be said to have a momentary dipole?
The atom is electrically neutral, because it has an equal number of protons and electrons, but the
electrons are all on one side of the atom, so a dipole (uneven distribution of charge) is created. It is
temporary, because the electrons continue to move.
30. Based on your answer to #30, what do you think helps neutral atoms and molecules attract each other? An
uneven distribution of electrons at a given moment helps neutral atoms and molecules form dipoles
that hold the atoms and molecules together.
31. What causes a London dispersion force to occur between two atoms or molecules? A momentary imbalance
of electrons throughout the molecule.
32. How are London dispersion forces similar to dipole-dipole interactions? How are they different? They are
similar because they both involve the attraction of oppositely charged poles toward each other. They
are different, because the dipoles in London dispersion forces are only temporary, whereas dipoledipole interactions involve permanent dipoles in polar covalent molecules.
33. What is the difference between the formation of an ion and the formation of a momentary dipole? An ion is
created by the removal or addition of an electron to an electrically neutral atom, thereby giving it a
charge. A momentary dipole is created by the temporary imbalance of electrons within an electrically
neutral atom (the atom remains neutral).
34. The difference of electronegativity between hydrogen and bromine is 0.7, and the difference in electronegativity
between hydrogen and chlorine is 0.9. Which would exhibit stronger dipole-dipole interactions, HBr or HCl?
Justify your answer. HCl will exhibit stronger dipole-dipole interactions, because the dipole itself will be
stronger—the imbalance of charge within the molecule will be greater.
35. Neon has ten electrons, and krypton has eighteen electrons. Which element do you think has a greater chance
of forming a momentary dipole? Which element do you think exhibits greater London dispersion forces?
Krypton will exhibit greater London dispersion forces, because it has a greater number of electrons.
Therefore, there is a greater probability that its electrons will become imbalanced and create a
momentary dipole.
©HSPI – The POGIL Project Limited Use by Permission Only – Not for Distribution
Intermolecular Forces C1YvM
11