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Unit 2 Homework Packet-Atomic Theory
History of the Atom
Write the name of the scientist who is credited with the following experiments or discoveries.
1. Thompson__Discovered the electron
5. __Chadwick_ Discovered neutrons
2. _Rutherford_Discovered the nucleus
6. __Rutherford___ Did the Gold Foil Exp.
3. __DemocritusNamed particles atoms
7. __Dalton________ Said all atoms are same
for one element
4. __ThompsonUsed a cathode ray tube
8. __Thompson_________ Plum pudding model
State the subatomic particle that is described in each of the following statements.
9. __p_____+1 charge
12. __e_____found outside nucleus
10. __n_____ No Charge
13. ___p & n____found inside nucleus
11. ___e____-1 charge
14. ____e___least massive
Answer each of the following questions completely.
15. Draw a model of how we expect atoms to look. Be sure to include the location of subatomic
particles.
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16. How does the mass of an electron compare to a proton and neutron?
Electrons are much lighter and smaller in mass then protons and neutrons
17. Put the subatomic particles in order from the most massive to the least massive.
P, N, then electrons
18. Why has our idea of what the atom looks like changed so many times?
Science is discovering new things everyday!
19. Do you think our view of the atom will every change again? Why or why not?
Sure! You never know what the future can hold! **This is an opinion question**
What is an Atom?
1. How many protons are found in 12C? __6______ 13C? ___6_____ 13C- ? ___6_______
2. How many neutrons are founds in 12C? _6______
13C?
___7______ 13C- ? __7_______
3. How many electrons are found in 12C? __6______ 13C? ___6______ 13C- ? __7_______
4. Based on the data presented above,
a. What do all carbon atoms (and ions) have in common? same protons
b. What do all hydrogen atoms (and ions) have in common?
5. What is the significance of the atomic number? Where will you find it on the periodic table?
Number of protons; number found on top of each element
6. How is the mass number determined?
Number of protons and neutrons
7. What structural feature is different in isotopes of a particular element?
Nucleus (changing the number of neutrons)
8. What feature distinguishes a neutral atom from an ion?
The charge next to the element
9. Where is most of the mass of an atom, within the nucleus or outside of the nucleus? Explain your
reasoning. Within the nucleus since electrons have the least mass
10. Complete the chart below:
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Isotope
Atomic Number (Z)
Mass Number (A)
Number of Electrons
31P
15
31
15
18O
8
18
8
39K+
19
39
18
58Ni2+
28
58
26
12. What is the mass (in amu) of
a. one 1H atom? _______1.008_________________
b. one 12C atom? ______12.01_________________
14. How many electrons, protons, and neutrons are found in each of the following?
Atom or ion
Electrons
Protons
Neutrons
24Mg
12
12
12
23Na+
10
11
12
35Cl
17
17
18
35Cl-
18
17
18
56Fe3+
23
26
30
15N
7
7
8
16O2-
10
8
8
27Al3+
10
13
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Atomic Emission Spectrum of the Bohr Hydrogen Atom
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Photon: A particle of electromagnetic radiation with no mass that carries a quantum of energy.
Quantum (pl. quanta): “a packet of energy”; the amount of energy absorbed or released when an
electron moves between energy levels.
Ground State: lowest possible energy of an e-.
The principal quantum number (n) = 1. [Energy level = 1]
The most energy is released when electrons fall to the n=1 energy level.
As wavelength decreases, frequency increases.
As frequency increases, the energy of the electromagnetic radiation increases.
1) In which transition is the most energy released?
a. n = 3 to n = 2
b. n = 3 to n = 1
2) Which transition required the largest quanta of energy input?
c. n = 5 to n = 2
d. n = 1 to n = 3
Name___________________________________________________________________________ Date_____________________
a. n = 2 to n = 4
b. n = 1 to n = 2
c. n = 2 to n = 1
d. n = 4 to n = 1
3) a) What wavelength of light is produced during a transition from n = 5 to n = 2?
__________434______ nm = _________4.34x10-7______ m
b) What color is the light that is released? Color = _______Blue_______________
4) a) What wavelength of light is produced during a transition
from n = 3 to n = 2? _______656________ nm = ________6.56x10-7______________ m
b) What color of light does this correspond to? Color = ____Red__________
5) If violet light of wavelength 4.1 x 10-7 m is released, what transition did the electron make?
n = ___6_______ to n = ____2______
6) Put in order from lowest to highest frequency:
a) Radio waves, gamma rays, IR, X-rays, UV, Microwaves
Radio, microwaves, IR, UV, Xrays, Gamma
b) Blue, Red, Violet, Orange
Red, Orange, Blue, Violet
7) Put in order from lowest energy to highest energy:
- Gamma Rays, IR, Radio Waves, UV, Red light, Violet Light
Radio, IR, Red, Violet, UV, Gamma
Nuclear Chemistry:
Name the type of emission:
1. Uranium-234 To Thorium-230
Alpha
Alpha
5. Polonium-218 to Lead-214
2. Thorium-230 to Radium-226
Alpha
Alpha
6. Lead-214 to Bismuth-214
3. Radium-226 to Radon-222
Beta
Alpha
7. Bismuth-214 to Polonium-214
4. Radon-222 to Polonium-218
Beta
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Name___________________________________________________________________________
Date_____________________
8. Polonium-214 to Lead-210
Alpha
Beta
11. Polonium-210 to Lead-206
9. Lead-210 to Bismuth-210
Beta
Alpha
11. Bismuth-210 to Polonium-210
Write an equation for the following elements through the given emission type.
Alpha Decay:
Beta Decay:
1. Polonium-218
1. Lead-210
218
Po→4 2 He + 214Pb
2. Polonium-210
210
Po→4 2He + 206Pb
3. Radium-224
224
Ra→42He + 220Rn
4. Radon-219
219
Rn→42He + 215Po
210
Pb→0-1e + 210Bi
2. Lead-214
214
Pb→0-1e + 214Bi
3. Bismuth-210
210
Bi→0-1e + 210Po
4. Bismuth-214
214
Bi→0-1e + 214Po
Half Lives
1. If gallium-68 has a half-life of 68.3 minutes, how much of a 10mg sample is left after two half-lives?
10/2 = 5/2=2.5 mg
2. If the passing of five half-lives leaves 25.0mg of a strontium-90 sample, how much was present in the
beginning?
25 mg x2=50x2=100x2=200x2=400x2= 800 mg
3. Manganese-56 is a beta emitter with a half-life of 2.6hr. What is the mass of manganese-56 in a 1mg
sample of the isotope after 10.4hr
2.6x2=5.2x2=10.4 (2 half lives)
1 mg/ 2=.5/2= .25 mg
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Name___________________________________________________________________________ Date_____________________
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Study Guide
1. Compare the mass of an electron, neutron, and proton
Protons and neutrons have the same mass, electrons are less mass
2. A neutral atom of Aluminum has how many electrons? What would happen if it gained 2 electrons?
What if it lost 3 electrons?
Al = 13 electrons
Al-2= 15 electrons
Al+3= 10 electrons
3. To change the identity of an atom, you have to change the number of __protons_______.
4. What atom is this: 18 Protons, 19 Neutrons, and 18 electrons?
Argon-37
5. How many total electrons are in Na+1?
10
6. What is an Ion?
Element with a charge (+ or -)
7. If an ion has 7 protons, 90 neutrons, and a +3 charge, what is its atomic number?
7 (atomic number = # of protons)
8. What was the purpose of the flame lab we did in class?
When an electron travels back to the ground state, it emits different forms of waves. In the lab, they
emitted different forms of color. The red color emits the least amount of energy while violet has the
most. By checking the colors of the flame will help identify the different elements on the periodic table.
9. Neutral atoms of the same element can have a different number of __neutrons________.
10. Which atom has 13 protons?
Aluminum
11. How many protons are in Au+?
79
12. What is the mass number for Calcium-42?
42
13. The atoms mass is in the ___nucleus______, which is made of __protons______and __neutrons_______.
14. Give the atomic symbol for the atom that has 11 protons, 12 neutrons, and 10 electrons.
23
+1
11Na
15. List the subatomic particles with their charges.
Protons (+), neutrons (0), electrons (-)
16. How many electrons are in the following a. B3+
a. 2
b. 10 c.7 d. 4
b. Al3+
c. N
d. N3+
17. What is an isotope?
Same element but different mass number (different number of neutrons)
Name___________________________________________________________________________ Date_____________________
18. Who discovered the charge of an electron?
JJ Thompson
19. If you change the electrons of an atom you also change the ____charge__________.
20. How many protons, neutrons, and electrons are in 48Cr+2?
p=24, n=24, e=22
21. Carbon-14 has more __neutrons_____ than Carbon-12.
22. What is transmutation?
Changing the element
23. Describe the two orbitals of 97 nm based on the Bohr diagram.
n=4 to n=1
24. If carbon as 15.0% of 12 C, 15.0% of 13C, and 70% of 14C, what is the average atomic mass (amu) of carbon?
(15x12) + (15x13) + (70x14) = 13.55 amu
100
25. Label the following diagram with the appropriate decays of each element.
Alpha
Beta
.
Alpha
Alpha
Alpha
Alpha
Alpha
Beta
Alpha
Beta
Alpha
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