SCH3U & SCH4C – Nomenclature & Intermolecular Forces Review Guide
This review guide covers bonding, intermolecular forces, chemical nomenclature, and molecular polarity. Use it to prepare for the upcoming quiz and test.
Part A — Atomic & Molecular Concepts
Define ionization energy.
Answer: TThe energy required to remove an electron from a gaseous atom or ion.
Define electron affinity.
Answer: The change in energy when an electron is added to a neutral atom in the gaseous state to form a negative ion.
Which element would have the highest ionization energy: Na, Mg, Cl, or K?
Answer: Cl (Chlorine). Ionization energy generally increases across a period and decreases down a group.
Identify which molecules can exhibit hydrogen bonding and explain why.
Answer: Molecules with H directly bonded to N, O, or F (e.g., H₂O, NH₃, HF). This occurs due to the high electronegativity of N, O, or F, creating strong partial charges that lead to strong dipole-dipole interactions.
List the three main types of intermolecular forces from weakest to strongest.
Answer: London Dispersion Forces (LDF), Dipole-Dipole forces, Hydrogen Bonding.
Why do ionic compounds tend to have higher melting points than molecular compounds?
Answer: Ionic compounds are held together by strong electrostatic forces between oppositely charged ions in a crystal lattice, requiring a large amount of energy to break. Molecular compounds are held by weaker intermolecular forces.
Compare the polarity of K–Br vs. K–Cl bonds. Which is more polar and why?
Answer: K–Cl is more polar. Chlorine (Cl) is more electronegative than Bromine (Br), leading to a larger electronegativity difference with Potassium (K).
Compare the polarity of H–Cl vs. H–Br bonds.
Answer: H–Cl is more polar. Chlorine (Cl) is more electronegative than Bromine (Br), leading to a larger electronegativity difference with Hydrogen (H).
Why do polar molecules usually have higher boiling points than nonpolar molecules?
Answer: Polar molecules have stronger intermolecular forces (dipole-dipole interactions, hydrogen bonding) compared to nonpolar molecules (London Dispersion Forces). More energy is required to overcome these stronger forces.
What is the main intermolecular force between CO₂ molecules? Explain your reasoning.
Answer: London Dispersion Forces (LDF). Although C=O bonds are polar, CO₂ is a linear molecule, and the bond dipoles cancel, making it nonpolar overall.
Part B — Lewis Structures, Shapes & Bond Types
Draw the Lewis structure for CH₄ and describe its molecular shape.
Answer: Lewis structure: Carbon with four single bonds to hydrogen atoms. Shape: Tetrahedral.
Is CO₂ polar or nonpolar? Justify using shape and bond polarity.
Answer: Nonpolar. The C=O bonds are polar, but the molecule's linear (
A
X
2
AX
2
) shape causes the two bond dipoles to cancel each other out.
Is NH₃ polar or nonpolar? Explain why.
Answer: Polar. The N-H bonds are polar, and the molecule has a trigonal pyramidal shape due to the lone pair on nitrogen. The bond dipoles do not cancel out.
Identify the bond type in NaCl and explain why it forms.
Answer: Ionic bond. It forms between a metal (Na) and a nonmetal (Cl) with a large electronegativity difference, leading to electron transfer from Na to Cl to form
N
a
+
Na
+
and
C
l
−
Cl
−
ions.
Identify the bond type in HF and explain its polarity.
Answer: Polar covalent bond. It forms between two nonmetals with a significant electronegativity difference (F is much more electronegative than H), resulting in unequal sharing of electrons.
Determine the bond type in CH₄ and classify it as polar or nonpolar.
Answer: Covalent bonds (specifically polar covalent, but often considered nonpolar for overall molecular polarity). The molecule itself is nonpolar due to its symmetrical tetrahedral shape where bond dipoles cancel out.
Explain the type of bond in BeF₂ and its polarity.
Answer: Polar covalent bonds (Be-F). The molecule itself is nonpolar because it has a linear shape (
A
X
2
AX
2
) and the two Be-F bond dipoles cancel each other out.
Which of these compounds has only London dispersion forces: H₂O, NH₃, CO₂, or HCl?
Answer: CO₂. H₂O and NH₃ have hydrogen bonding, HCl has dipole-dipole forces. CO₂ is nonpolar overall.
Which of the following molecules is nonpolar overall: H₂O, CO₂, NH₃, or HCl?
Answer: CO₂.
What two factors determine molecular polarity?
Answer:
Bond polarity: The presence of polar bonds within the molecule.
Molecular geometry/shape: The arrangement of these polar bonds in three-dimensional space, determining if bond dipoles cancel out.
Part C — Name These Compounds (Formula → Name)
Name MnSO₄.
Answer: Manganese(II) sulfate
Name CaCO₃.
Answer: Calcium carbonate
Name SO₂.
Answer: Sulfur dioxide
Name H₂SO₄.
Answer: Sulfuric acid
Name BeCl₂.
Answer: Beryllium chloride
Name CBr₄.
Answer: Carbon tetrabromide
Name (NH₄)₃P.
Answer: Ammonium phosphide
Name FePO₄.
Answer: Iron(III) phosphate
Name KHSO₄.
Answer: Potassium hydrogen sulfate (or Potassium bisulfate)
Name NaH₂PO₄.
Answer: Sodium dihydrogen phosphate
Part D — Write the Correct Formula (Name → Formula)
potassium hypochlorite.
Answer: KClO
magnesium oxide.
Answer: MgO
dinitrogen pentoxide.
Answer:
N
2
O
5
N2O5
copper(I) sulfate pentahydrate.
Answer:
C
u
2
S
O
4
⋅
5
H
2
O
Cu2SO4⋅5H
2
O
sodium perchlorate.
Answer:
N
a
C
l
O
4
NaClO
4
lithium carbonate.
Answer:
L
i
2
C
O
3
Li2CO3
copper(II) phosphate.
Answer:
C
u
3
(
P
O
4
)
2
Cu3(PO4)
2
potassium hydrogen sulfite.
Answer:
K
H
S
O
3
KHSO
3
titanium(II) bromate.
Answer:
T
i
(
B
r
O
3
)
2
Ti(BrO3)2
sulfur trioxide.
Answer:
S
O
3
SO
3
Part E — Application & Challenge
Which of the following compounds has the highest boiling point: CH₄, NH₃, CO₂, or H₂? Explain.
Answer: NH₃. It can form hydrogen bonds, which are the strongest intermolecular forces among the options.
Which of these molecules exhibits the strongest dipole–dipole interaction?
Answer: This question lacks specific options. If referring to a list like H₂O, NH₃, HCl, then H₂O or NH₃ would exhibit strong dipole-dipole interactions (specifically, hydrogen bonding), which are stronger than typical dipole-dipole forces like in HCl.
Identify one compound that contains a transition metal and explain how you can tell.
Answer: MnSO₄ (Manganese(II) sulfate). Manganese (Mn) is a transition metal located in the d-block of the periodic table, and its name includes a Roman numeral to indicate its variable charge.
Which of these compounds is an acid? What makes a compound an acid?
Answer: H₂SO₄ (Sulfuric acid). An acid is typically a compound that donates a proton (
H
+
H
+
ion) in solution.
Describe how ionic compounds conduct electricity in solution.
Answer: When ionic compounds dissolve in water, their ions separate (dissociate) and become mobile. These mobile, charged ions (
c
a
t
i
o
n
s
cations and
a
n
i
o
n
s
anions) are then free to move and carry electrical charge, thus conducting electricity.
What is a hydrate? Provide one example and its chemical name.
Answer: A hydrate is an ionic compound that has water molecules chemically bonded to its crystal structure.
Example:
C
u
S
O
4
⋅
5
H
2
O
CuSO4⋅5H2O
Chemical Name: Copper(II) sulfate pentahydrate
Explain metallic bonding and describe how it differs from ionic and covalent bonding.
Answer:
Metallic bonding: Involves a "sea" of delocalized valence electrons shared among a lattice of positively charged metal ions. Electrons are free to move throughout the structure.
Difference from Ionic: Ionic bonding involves electron transfer to form discrete ions. Metallic bonding involves delocalized sharing of electrons.
Difference from Covalent: Covalent bonding involves localized sharing of electrons between specific pairs of atoms. Metallic bonding's electrons are delocalized over many atoms.
Identify which of these compounds contains only nonmetals: NaCl, CO₂, MgO, or Fe₂O₃.
Answer: CO₂ (Carbon and Oxygen are both nonmetals).
Explain why many binary ionic compounds end in “-ide.” Give two examples.
Answer: Binary ionic compounds are made of a metal cation and a nonmetal anion. When a simple anion (from a single nonmetal element) forms, its name ends in "-ide" to indicate it's a monatomic anion.
Examples: Chloride (
C
l
−
Cl
−
) in NaCl, Oxide (
O
2
−
O
2−
) in MgO.
Which molecule is likely nonpolar overall: H₂O, CO₂, NH₃, or SO₂? Explain your reasoning.
Answer: CO₂. It has a linear shape, and its polar C=O bonds are symmetrical, causing their dipoles to cancel out.