Download Review Topic 3: Elements, Radioactivity, and the Periodic Table

5/17/2015
Review Topic 3: Elements, Radioactivity, and the Periodic Table
Name: Score: 19 / 19 points (100%)
Review Topic 3: Elements, Radioactivity, and the Periodic Table
Multiple Choice
Identify the choice that best completes the statement or answers the question.
A 1. The element chlorine exists as two naturally occurring isotopes. Cl­35 occurs 75% of the
time and Cl­37 occurs 25% of the time. Which of the following calculations should be used
to calculate the correct average atomic mass of chlorine?
a. (35 amu x 0.75) + (37 amu x 0.25)
c. (35 amu x 3) + 37 amu
3
b. (35 amu x 3) + 37 amu
d. 35 amu ­ 37 amu
2
2
ANSWER: A
We learned each amu x %, add them together then divide by 100. The correct
answer here just divided each percent by 100 first.
POINTS: 1 / 1
B 2. Radioactive iodine­131 has a half­life of eight days. The amount of a 200.0 gram sample
left after 32 days would be —
a. 6.25 g
c. 25.0 g
b. 12.5 g
d. 50.0 g
ANSWER: B
Total time = # x half life time
32 = # x 8
# = 4, so we need to divide 200.0 grams by 2 four times.
200/2/2/2/2 = 12.5
POINTS: 1 / 1
A 3. Which of these describes a tendency for atomic radii as displayed on the periodic chart?
a. Atomic radii decrease left to right across a period.
b. Atomic radii increase left to right across a period.
c. Atomic radii decrease top to bottom down a group.
d. Atomic radii increase, then decrease from top to bottom down a group.
ANSWER: A
radii gets bigger going down and smaller going across (left to right), so Fr is
biggest and F is smallest. (Opposite trend of electronegativity)
POINTS: 1 / 1
C 4. How does the radioactive isotope C­14 differ from its stable counterpart C­12?
a. It has a different number of protons and two less neutrons than C­12.
b. It has the same number of protons and two more electrons than C­12.
c. It has the same number of protons but two more neutrons than C­12.
d. It has a different number of protons and two more neutrons than C­12.
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Review Topic 3: Elements, Radioactivity, and the Periodic Table
ANSWER: C
What makes isotopes ­ neutrons
It has a different number of protons and two less neutrons than C­12. ­ different protons would
change it from C
It has the same number of protons and two more electrons than C­12. ­ different electrons
would make it an ion, not an isotope
It has the same number of protons but two more neutrons than C­12. ­ two more neutrons
would make it 2 heavier and make it 14. It has a different number of protons and two more neutrons than C­12 .­ different protons
would change it from C
POINTS: 1 / 1
D 5. Chlorine forms a 1– ion. How many electrons does a chloride ion have?
a. 1
c. 17
b. 16
d. 18
B 6. ANSWER: D
Normally, Cl has 17 electrons. ­1 means that it has gained another electron,
which are negative to make the total 18
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6. Which of the groups below has the electron dot structure shown above?
a. Noble gases
c. Alkali metals
b. Halogens _
d. Transition elements
ANSWER: B
Looking for a group with 7 valence electrons sends us to group 17 ­ the
halogens
POINTS: 1 / 1
A 7. Which of these elements is the most chemically active?
a. F
c. Br
b. Cl
d. I
A 8. ANSWER: A
Fluorine is the most electronegative which makes it the most reactive. Francium, the least electronegative, believe it or not is up there for reactivity as
well.
POINTS: 1 / 1
Element Protons Neutrons Electrons
1
20
20
20
2
40
40
40
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Review Topic 3: Elements, Radioactivity, and the Periodic Table
3
4
20
20
10
20
10
40
Which above represents an atom of calcium?
a. 1
c. 3
b. 2
d. 4
ANSWER: A
Calcium has an atomic number of 20. which means it would have 20 protons
and since it is an atom and not an ion, the electrons would be equal to the
protons.
POINTS: 1 / 1
A 9. From left to right across a period, what change is occurring within the atomic nuclei?
a. A proton is gained
c. A neutron is lost
b. An electron is gained
d. The electron cloud size is decreasing
ANSWER: A
Electrons and the electron cloud are not in the atomic nuclei and neutrons
would be gained.
POINTS: 1 / 1
B 10. A scientist has found the following isotope of oxygen
How many neutrons are present in this isotope?
a. 8
c. 19
b. 11
d. 27
ANSWER: B
Top number is the mass number, bottom number is the atomic number. Neutrons = mass number ­ atomic number = 19­8 = 11
POINTS: 1 / 1
A 11. The elements that are characterized by the presence of an incomplete d sublevel are called ­
a. transition elements
c. halogens
b. alkali earth metals
d. lanthanoids
ANSWER: A
transition elements ­ incomplete d
alkali earth metals ­ incomplete s
halogens ­ incomplete p
lanthanoids ­ incomplete f
POINTS: 1 / 1
D 12. The net charge on an aluminum ion is +3 because there are ­
a. 10 protons and 13 electrons in the atom
b. 13 protons and 10 neutrons in the nucleus
c. 10 neutrons and 13 electrons in the atom
d. 13 protons and 10 electrons in the atom
ANSWER: D
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Review Topic 3: Elements, Radioactivity, and the Periodic Table
Al has 13 protons (atomic number) and since it is +3, there has to be 3 more
protons than electrons. Changing the neutrons would only change the mass
and the isotopes.
POINTS: 1 / 1
A 13. How many protons, neutrons, and electrons are in a neutral atom of sodium?
a. 11 p+, 12 n0, 11 e­
c. 12 p+, 11 n0, 12 e­
+
0
­
b. 11 p , 11 n , 12 e
d. 12 p+, 11 n0, 11 e­
ANSWER: A
Sodium is atom #11, which means it has 11 protons and since it is neutral it
needs 11 electrons.
POINTS: 1 / 1
A 14. Which conclusion can be made from these data?
Characteristics of Different Sulfur (S) atoms
1
2
3
4
Protons
16
16
16
16
Neutrons
16
17
18
20
Electrons
16
16
16
16
a. Different isotopes of sulfur (S) have different number of neutrons.
b. Different polymers of sulfur (S) have different numbers of electrons.
c. All ions of sulfur (S) have the same mass.
d. All particles of sulfur (S) have the same mass number
ANSWER: A
Changing neutrons results in isotopes which is what we see in this chart (the
neutrons changed)
Different electrons result in ions not polymers
If the neutrons are different in the ions, then the masses would change
Once again, if the neutrons are different then the mass number would be
different
POINTS: 1 / 1
A 15. Which element has atoms that most likely have the greatest shielding effect?
a. Barium (Ba)
c. Calcium (Ca)
b. Strontium (Sr)
d. Magnesium (Mg)
ANSWER: A
The more electrons you have and the bigger the atom (more energy levels) the
more shielding it would have.
POINTS: 1 / 1
B 16. Which element has 16 neutrons, 15 protons, and 15 electrons?
a. Sulfur (S)
c. Gallium (Ga)
b. Phosphorus (P)
d. Zinc (Zn)
ANSWER: B
The important subatomic particle here is the proton. The number of protons =
atomic number, which tells you the element is phosphorus (atomic number 15).
POINTS: 1 / 1
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Review Topic 3: Elements, Radioactivity, and the Periodic Table
A 17. Consider any set of three elements in the same period on the periodic table. For which
characteristics is the average for the three elements always equal to the value of the middle
element?
a. Atomic number
c. Number of neutrons
b. Atomic mass
d. Number of isotopes
B 18. ANSWER: A
Since atomic number always increases by 1 as you increase elements, this is
the only characteristic that is listed that is consistent enough to have the
average work.
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What is the half­life of Americium­242?
a. 11 hours
b. 16 hours
c. 32 hours
d. 64 hours
ANSWER: B
A half­life is the amount of time required to lose half of your material. According to the graph, it takes 16 hours to go from 80 to 40.
POINTS: 1 / 1
Multiple Response
Identify one or more choices that best complete the statement or answer the question.
Directions: Click on the correct answers.
19. According to the periodic table of the elements, which elements belong to the same period?
a. Aluminum
d. Arsenic
b. Germanium
e. Gallium
c. Antimony
RESPONSE: B,D,E
ANSWER: B,D,E
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Review Topic 3: Elements, Radioactivity, and the Periodic Table
POINTS: A row is known as a period, so we need all the elements in the same row.
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