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Guide: Atomic Theory and Structure (Including the mole) KEY
Identify the three subatomic particles: a.
protons b.
electrons c. neutrons
The protons and
neutrons
are located in the nucleus of the atom.
The
electrons
are located on the electron cloud outside the nucleus.
Which subatomic particle(s) make up the majority of the mass of an atom?
Protons & neutrons
What is an isotope?
Atoms of the same element with different numbers of neutrons
How is the mass number calculated? Weighted average of all isotopes
The number of protons is given by the
atomic
number .
The number of electrons is equal to the number of
protons
.
Fill in the following table:
Nuclear
Name
Mass
Protons
Neutrons
Electrons
Symbol
Number
16
O
Oxygen-16
16
8
8
8
8
17
O
8
18
O
8
80
Br
35
40
K
19
55
Fe
Oxygen-17
17
8
9
8
Oxygen-18
18
8
10
8
Bromine - 80
80
35
45
35
Potassium40
Iron-55
40
19
21
19
55
26
29
26
26
10. Magnesium has 3 isotopes. Magnesium-24; Magnesium-25; Magnesium-26. What would each of these
isotopes have in common? Same element (Mg), same numbers of protons & electrons. What would be
different for each isotope? Different numbers of neutrons, so different masses.
11. Which subatomic particle determines the identity of an atom?
proton
12. What determines the identity of the isotope? Number of neutrons
13. Fill in the following table
Scientist
Accomplishments/Contributions to our
knowledge of the atom
Democritus
1st atomic theory around 400 B.C.
Dalton
Accepted atomic theory
Thomson
Discovered the electron
Millikan
Determined charge of an electron
Rutherford
Atom is empty space with central nucleus core
Goldstein
Discovered the proton inside the nucleus
Chadwick
Discovered the neutron
Bohr
Planetary model of the atom
Experiment
none
Cathode ray tube
Oil drop experiment
Gold Foil experiment
14. Describe or draw a picture of the model of the atom that each of the following scientists developed:
Dalton:
Thomson
Bohr
15. Draw the Bohr diagram for each of the following isotopes:
Carbon-12
Calcium-40
Magnesium-24
Sulfur-32
Boron-11
16. The element selected as the standard for the atomic mass scale was _Carbon-12________.
17. There are ____6.02 x 1023__________________ atoms of cesium in one mole.
18. One atom of cesium has a mass of __133_________ amu.
19. One mole of cesium has a mass of __133 grams_________.
20. Two moles of nitrogen have a mass of ___28 g________.
21. Two moles of nitrogen contain ______1.2 x 1024__________________atoms.
22. Another name for the number of objects in a mole is _Avogadro’s_______ number.
Multiple Choice: Identify the letter of the choice that best completes the statement or answers the question.
1.
____ 6.02 x 1023 is called _____ number.
a. Avogadro’s
b. Newton’s
2. ____ There are 6.02 x 1023 atoms in one ____ .
a. mole
b. Newton
c. Aristotle’s
d. Planck’s
c. amu
d. kilogram
3. ____ The mass in grams of one mole of any pure substance is called its ____ mass.
a. atomic
b. formula
c. molar
d. molecular
4. ____ If 24 g of carbon is measured on a balance, how many atoms have been indirectly counted?
a. 2
b. 24
c. 6.02 x 1023
d. 12.04 x 1023
5. ____ Which element has a molar mass of 31 g/mole?
a. Potassium
b. Phosphorus
c. Gallium
d. Palladium
6. ____Which is the mass of an atom of calcium?
a. 20 amu
b. 20 g
d. 40 g
c. 40 amu
Conversions:
1. 4.00 moles of Bromine is equal to how many grams of Bromine?
4.00 moles Br x 80 g Br = 321 g Br
1
1 mole Br
2. 46.0 grams of Sodium is equal to how many atoms of Sodium?
46.0 g Na x 1 mole Na x 6.02 x 1023 atoms Na = 12.0 x 1023 atoms Na (or 1.20 x 10
1
23 g Na
1 mole Na
3. 18.04 x1023 atoms of Boron is equal to how many moles of Boron?
18.04 x1023 atoms B x 1 mole B = 3.000 moles B
1
6.02 x 1023 atoms B
4. 3.01x1023atoms of Lithium is equal to how many grams of Lithium?
3.01x1023atoms Li x
1 mole Li
x
7 g Li =
3.50 g Li
23
1
6.02 x 10 atoms Li 1 mole Li
5. 4.0 moles of Argon is equal to how many atoms of Argon?
4.0 moles Ar x 6.02 x 1023 atoms Ar = 24 x 1023 atoms Ar (or 2.4 x 10
1
1 mole Ar
24
)
24
)