CHEM 2000 – Introduction to Chemistry
Week 4 Problem Set
50 points total
1. Denote whether the following statements about molecules are true or false by writing T or F. (3 pts)
a. An element cannot be a molecule.
b. A molecule must have at least one chemical bond.
c. A molecule must have at least three atoms.
2. Write the molecular formulas of the following compounds, e.g. in the format H2O2. (modified from
CAF2e 2.7.30, 6 pts)
a.
b.
c.
3. Which of the following atoms would be expected to form negative ions in diatomic (2-atom) ionic
compounds and which would be expected to form positive ions? Br, Ca, Na, N, F, Al, Sn, S, Cd
(CAF2e 4.1.4, 9 pts)
Negative ions:
Positive ions:
4. Provide pairs of atoms that meet the following conditions regarding electronegativity and bonding,
using an electronegativity table to guide your thinking. (6 pts)
a. Two atoms that are not the same element but would form a pure covalent bond
b. A main-group metal (alkali or alkaline earth metal) and a main-group nonmetal that would form
a covalent bond
c. Two atoms in the same period (row) that would form an ionic bond
5. Write Lewis structures for the following molecules. (modified from CAF2e 4.4.39, 12 pts)
a. Br2
b. H2S
c. CN- (hint: the negative charge is on the carbon atom)
d. H2CNH (this molecular formula format tells us that the C has 2 H atoms on it and the N has 1 H)
6. What feature of a Lewis structure can be used to tell if a molecule’s (or ion’s) electron-pair geometry
and molecular structure will be identical? (CAF2e 4.6.76, 4 pts)
7. Using VSEPR theory, identify the electron pair geometry of the following molecules or ions. If a
tetrahedral electron pair geometry would have a different molecular structure, name the molecular
structure also. (modified from CAF2e 4.6.82, 10 pts)
a. IF6+
b. H3O+
c. BH3 (B has 6 valence electrons in this molecule)
d. SF2
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