Chemistry--Unit 1: Atomic Structure and the Periodic Table
Practice Problems
I. Atoms
1) 100,000,000 copper atoms would form a line 1 cm long. How long would a line
formed by 1 x 107 copper atoms be? Express your answer in millimeters.
1  10 8 Cu atoms 1  10 7 Cu atoms

10 mm
? mm
?  1 mm
II. Structure of the Atom
2) A sulfur-32 atom contains 16 protons, 16 neutrons, and 16 electrons. What is the
mass, in grams, of a sulfur-32 atom?
+
16 × 1.67262 × 10‒24 g
16 × 1.67493 × 10‒24 g
16 × 9.10939 × 10‒28 g
5.35754 × 10‒23 g
or
16 × 1.67 × 10‒24 g
16 × 1.67 × 10‒24 g
16 × 9.11 × 10‒28 g
5.34 × 10‒23 g
or
32 × 1.67 × 10‒24 g
(electrons negligible)
5.34 × 10‒23 g
or
7 × 1.67 × 10‒24 g
(electrons negligible)
1.17 × 10‒23 g
3) What is the mass in grams of a lithium-7 atom?
+
3 × 1.67262 × 10‒24 g
4 × 1.67493 × 10‒24 g
3 × 9.10939 × 10‒28 g
1.17203 × 10‒23 g
or
3 × 1.67 × 10‒24 g
4 × 1.67 × 10‒24 g
3 × 9.11 × 10‒28 g
1.17 × 10‒23 g
4) The mass of a neutron is 1.67 x 10–24 g. Approximately what number of neutrons
would equal a mass of one gram?
1 gram
1.67  10 24 grams

1 neutron
? neutrons
?  5.99  10 23 neutrons
III. Distinguishing Between Atoms
5) How many protons are found in an atom of each of the following?
a. boron (5)
b. sulfur (16)
c. neon (10)
d. lithium (3)
6) Complete the table for the following elements:
Chemistry--Unit 1: Atomic Structure and the Periodic Table
Practice Problems
Element
Name
Number
of
Electrons
25
Number
of
Neutrons
30
Atomic
Number
Mass
Number
Manganese
Number
of
Protons
25
Element
Symbol
25
55
55
25
Sodium
11
11
12
11
23
Bromine
35
35
45
35
80
23
11
80
35
Yttrium
39
39
50
39
89
Arsenic
33
33
42
33
75
75
33
Actinium
89
89
138
89
227
227
89
Mn
Na
Br
89
39
Y
As
Ac
7) How many neutrons are in each atom?
a. 23Na (12)
b. 238U (146)
c. 81Br (46)
d. 19F
(10)
8) The two most abundant isotopes of carbon are carbon-12 (mass = 12.00 amu) and
carbon-13 (mass = 13.00 amu). Their relative abundances are 98.9% and 1.10%,
respectively. Calculate the atomic mass of carbon.
12.00 × 98.9 = 1186.8
13.00 × 1.10 = 14.3
1201.1
+
÷ 100 = 12.01 amu’s or μ
9) Element X has two isotopes: X-100 and X-104. If the atomic mass of X is 101 amu,
what is the relative abundance of each isotope in nature?
100 × A =
104 × B =
?
?
10,100
+
÷ 100 = 101 amu’s or μ
or, more “mathy”, 100A + 104B = 10,100
One equation with two unknowns, solve with substitution, but need a second
equation. A and B are percentages in nature of element 101, so A + B must = 100
(or 100 ‒ B = A).
So,
100(100 ‒ B) + 104B = 10,100
10,000 ‒ 100B + 104B = 10,100
4B = 100
B = 25%, A = 75%
Chemistry--Unit 1: Atomic Structure and the Periodic Table
Practice Problems
*Note that guess and check will also work to solve this problem, but will take
much longer!
IV. The Periodic Table: Organizing the Elements
10) Which element below should have chemical properties similar to fluorine (F)?
a. Li
b. Si
c. Br
(c. Br—in same chemical family on periodic table)
d. Ne
11) Identify each element as a metal, metalloid, or nonmetal.
a. fluorine
(nonmetal)
b. germanium (metalloid)
c. zinc
(metal)
d. phosphorus (nonmetal)
e. lithium
(metal)
12) Which of the following is not a transition metal?
a. magnesium
(a. Magnesium)
b. titanium
c. chromium
d. mercury
13) Name two elements that have properties similar to those of the element potassium.
(Any 2 of lithium, sodium, rubidium, cesium, francium)
14) All elements of the periodic table can be divided into three broad classes. What are
these classes and how do they differ?
(metals, nonmetals, metalloids)
METALS
good conductors of heat and electricit y
shiny in appearance (have luster)
malleable and duct ile
high tensile strength
high melt ing and bo iling points
high densit ies
METALLOIDS
vary in properties between metals and nonmetals
NONMETALS
poor conductors of heat and electricit y
dull in appearance (lack luster)
brittle
cannot withstand stress
low melt ing and bo iling po ints
low densit ies