1) Copy and complete the table. All below are in elemental form, not ions.
Symbol /
Atomic
Notation
number
lb0
8
14c
s
5B
W
#of
#of
# of
protons
electrons
neutrons
b
li
!</
b
/y
V\
14
55
25
5
74
74
74
Krypton-84
Mass
number
-bio
/
<?
8
A
15
30
//t
4f
7.(0
2) List the number of protons, neutrons, and electrons in each pair of isotopes.
a. ln,lu b. Ca Ca C. lSe Se
3) The atomic masses of elements are not whole numbers. Explain why.
4) Differentiate between (average) atomic mass and mass number.
5) Draw the notation for an atom composed of 16 protons, 16 electrons, and 16 neutrons.
A/
4 Li 3
: j) lie*
1 10
7U 3 4
3
p
r4
bl
10 I
,7 s
10 v\
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CA
i
4j M
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o
3 MU 31
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cyplts 1 < 11 ews m (te. tiore)
d- plie- -fo an 8r .
5 SulDr-32.; 3aS ; 5 ; S-31..
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6) What parts of Dalton s atomic theory do not agree with the current theory of the atom?
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7) What evidence did Thomson use to claim his discovery of negatively charged particles
being present in atoms? How did he determine there were corpuscles (electrons) in all
matter? e +yipieJ jOrodvCc L b ano of ni at vdy kar ejL feAictieJ,
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8) The diagram shows gold atoms being bombarded with fast-moving alpha particles. he
large light gray spheres represent gold atoms.
a)
b)
c)
What do the small dark gray spheres represent? ftvclti vanishi y
List at least two characteristics of the small dark gray spheres. S uttt / vi c J •
Which subatomic particl cannot be found in the area represented by the large light
gray spheres? >r H>iof *
9) Given Rutherford s nuclear model of the atom, discuss and compare the relative size and
density of an atom with the size and density of its nucleus.
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Though disproven shortly after being po ited, the Bohr planetary model of the atom is a useful way to model subatomic
particles of an atom. Use the Bohr model at right to answer the next 6 questions.
10)
Draw five protons in the nucleus of the atom. Label them
with their charge.
11)
12)
Draw six neutrons in the nucleus of the atom.
13)
Draw three electrons in the second energy level and label
them with their charge.
14)
15)
What element is represented by the diagram? |)OfOr\
Draw two electrons in the first energy level and label them
with their charge.
What makes the Bohr model a poor representation of an
actual atom?
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is WT a , Rw S of e
16)
.
How many nitrogen-14 atoms would you need to place on the right pan to balance the
three calcium-42 atoms on the left pan of the atomic balance below? Describe the
method you used to determine your answer, including any calculations.
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17)
Name two ways isotopes of an element differ.
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18)
The 4 isotopes of mysterium are shown below, each with its % by mass abundance and
the composition of its nucleus. Using these data, calculate the atomic mass of
mysterium.
82p+ 122n° 1.37% ; 82p+ 124n° 26.26%
82p+ 125n° 20.82% ;82p+ 126n° 51.55%
e-lo >
19) Thallium has two isotopes, thallium-203 and thallium-205. Thallium s atomic number
is 81 and its atomic mass is 204.38 amu. Which statement about the thallium isotopes
is true? Correct the false statements. . . # 305
fALSS a) There is more thallium-203 than thallium-205 in nature.
b) Atoms of both isotopes have 81 protons. &
ftuS E c) Thallium-205 atoms have fewer neutrons. i More .
d) The most common type of thallium has a mass of 204.38 amu.
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20) Calculate the average atomic mass of element X, given that it consists of the following
percentages of isotopes with masses shown:
67 X, 50.00%, 66.941 amu
69X, 30.00%, 68.939 amu
71X, 20.00%, 70.937 amu <k\\ Si fijs
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2 7*2.12.
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EXTENSION
1) Lithium has two naturally occurring isotopes. Lithium-6 has an atomic mass of 6.015
amu; lithium-7 has an atomic mass of 7.016 amu. The average atomic mass of lithium is
6.941 amu. What is the percentage of naturally occurring lithium-7?
2) Use the mass spectrometry data below to determine the approximate atomic weight of
zirconium.
100
Z
: 3
•• I ? /.
)
o
§
¦o
§ 50
JO
Zr-90
Zr 17- .
<U
>
!
{£
Zr Ml'
Zr-92 Zr-94
Zr-91
Zr-96
i 1 I i I i n
la
7~r
•51/
90 92 94 96
Mass-to-charge ratio
ll.35
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are