Download Concepts to know for the Unit 3 test

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Chemistry: Unit 3 - Atoms
Test Review KEY
Concepts to know for the Unit 3 test:
1. Summarize the major experimental evidence that led to the development of various atomic models,
both historical and current.
2. Evaluate the limitations of using models to describe atoms.
a. Aristotle:
a. WRONG, four elements – earth, air, water, fire
b. Democritus:
a. Everything is made of small indivisible particles, coined “atomos”
c. John Dalton:
a. All matter is made of atoms
b. Compounds are combinations of 2+ kinds of atoms, atoms are rearranged in
chemical reactions
c. Atoms cannot be divided (FALSE because protons, neutrons, electrons exist)
d. All atoms of a given element are identical (FALSE because isotopes with different
# of neutrons exist),
e. Atoms cannot be destroyed (FALSE because nuclear reactions change identity of
atoms)
f. Billiard ball model of the atom (INCORRECT because no protons, neutrons, or
electrons)
d. JJ Thompson:
a. Cathode ray tube experiment
b. Discovered electron
c. Plum pudding model (INCORRECT because no nucleus)
e. Robert Millikan:
a. Oil drop experiment
b. Discovered charge-to-mass ratio of electron
f. Ernest Rutherford:
a. Gold foil experiment
b. Discovered nucleus
c. Planetary model (INCORRECT because no energy levels)
g. Niels Bohr:
a. Discovered energy levels for electrons
b. Bohr model
3. Discriminate between the relative size, charge, and position of protons, neutrons, and electrons in
the atom.
a. Discriminate between the relative size, charge, and position of protons, neutrons, and
electrons in the atom.
a. Proton: positive charge, 1 amu, found in nucleus
b. Neutron: no charge, 1 amu, found in nucleus
c. Electron: negative charge, 1/2000 amu, orbits nucleus
Chemistry – HOMEWORK
4. Generalize the relationship of proton number to the element’s identity.
a. # protons = atomic number = identifies the element
5. Relate the mass and number of atoms to the gram-sized quantities of matter in a mole.
a. 1 mole = 6.02 x 1023 particles (particles = atoms, molecules, doughnuts, etc.)
b. Atomic mass and molar mass are the same numbers, just different units
c. Determine atomic/molar mass from the periodic table
d. For a compound, add the masses of all the parts
a. H2O = 2H + O = 2(1.01) + 15.99 = 18.02
e. Atomic mass: units of amu, used for measuring the mass of a single particle (atom,
molecule, etc.)
f. Molar mass: units of g/mol, used for measuring the mass of a mole of particles
g. To convert moles  mass (g): multiply by molar mass (g/mol)
h. To convert mass (g)  moles: divide by molar mass (g/mol)
6. Use the periodic table to correlate the number of protons, neutrons, and electrons in an atom.
a. Atomic number: Number of protons
b. Mass number: Number of protons + number of neutrons
c. Number of electrons: Same as # of protons in neutral atom
a. # Electrons > # Protons  NEGATIVE charge
b. # Protons > # Electrons  POSITIVE charge
7. Compare the number of protons and neutrons in isotopes of the same element.
a. Isotopes: atoms with same number of protons and different number of neutrons
b. Hyphen notation: Name-Mass # (E.g.: Helium-4)
c. Nuclear symbol:
8. Recognize that radioactive particles and wavelike radiations are products of the decay of an
unstable nucleus.
a. Radioactive atoms decay through fission
b. Nuclear becomes unstable when it becomes too big
9. Interpret graphical data relating half-life and age of a radioactive
substance.
In the graph to the left, the half-life (time it takes to
lose 50% of the sample) is 7 seconds. In 21 seconds,
three half-lives will have passed and only 1/8 of the
original sample will remain.
Chemistry – HOMEWORK
10. Compare the mass, energy, and penetrating power of alpha, beta, and gamma radiation.
a. Alpha: Helium-4 nucleus, low penetrating power
b. Beta: Electron, intermediate penetrating power
c. Gamma: High-energy radiation, high penetrating power
11. Evaluate and report the effects of nuclear radiation on humans or other organisms.
a. Nuclear radiation can cause sickness, burns, death, etc.
Available on the Test:
 Periodic Table
 Calculator
1. What is the atomic mass of each of the following elements or compounds?
a. Nickel 58.693 amu
b. H2SO4 (sulfuric acid)
2(1.01) + 32.07 + 4(15.99) = 98.05 amu
2. What is the molar mass of each of the following elements or compounds?
a. Bromine
79.907 g/mol
b. NH3 (ammonia)
14.01 + 3(1.01) = 17.04 g/mol
3. How many moles are in 15.05 g cobalt, Co?
15.05 g Co | 1 mol Co
58.933 g
=
0.255 moles
4. How many grams are in 4.5 mol ozone (O3)? Hint: Calculate the molar mass of O3.
Molar mass ozone = 3(15.99) = 47.997 g/mol
4.5 mol O3 | 47.997 g = 215.99 g
1 mol
5. Os-182 has a half-life of 21.5 hours. How many grams of a 10.0 gram sample would have decayed after
exactly three half-lives?
10.0 g / 2 = 5.0 g / 2 = 2.5 g / 2 = 1.25 g
1st
2nd
3rd
Half-lives
Chemistry – HOMEWORK
6. Look at the following diagram and complete the information about this atom:
Atomic number: 2
Proton
Number of Protons: 2
Neutron
Number of Neutrons: 1
Number of electrons: 2
Mass Number: 3
Element name: Helium
Hyphen notation: Helium-3
Nuclear Symbol
3
2 He
7. Complete the following table
Element
Name
Nitrogen
Atomic
Number
Bromine
Uranium
Number
of
Neutrons
Number
of
Electrons
8
7
15
Nitrogen-15
20
22
18
42
Calcium-42
35
45
35
80
143
92
235
7
7
20
Calcium
Number
of Protons
35
92
92
Mass
Number
Hyphen
Notation
c. Planetary model
i. Rutherford
ii. Gold foil experiment
iii. Discovery of nucleus
d. Bohr model
i. Energy levels
ii. Hydrgogen line spectrum – my bad, we’ll do this
experiment in unit 4!
Chemistry – HOMEWORK
15
7 N
20
42
Ca2+
Bromine-80
80
35Br
Uranium-235
92
8. Sketch each model of the atom. Describe the discovery that led to each model.
a. Billiard ball model
i. John Dalton’s atomic theory
ii. Everything is made of atoms
iii. Atoms aren’t divisible
b. Plum pudding model
i. Thomson
ii. Cathode ray tube experiment
iii. Discovery of electron
Nuclear
Symbol
235
U
Practice Problems from the game:
1. What one number identifies an element?
a. Protons / Atomic number
2. What is the relationship between electrons and protons in a neutral atom?
a. Same number of each
3. Where are electrons located in an atom?
a. Orbiting outside
4. How many electrons can be held in the first energy level?
a. 2
5. How many electrons can be held in the second energy level?
a. 8
6. Where are protons located in an atom?
a. Nucleus, center
7. Where are neutrons located in an atom?
a. Nucleus, center
8. Write the atomic number for Chlorine
a. 17
9. Write the atomic number for Gold
a. 79
10. Write the atomic number for Lead
a. 82
11. Write the atomic number for Uranium
a. 92
12. Write the atomic number for Calcium
a. 20
13. Write the atomic number for Xenon
a. 54
14. Define isotopes
a. Atoms that have the same number of protons but different numbers of neutrons.
15. Define ions.
a. Charged particles due to gain or loss of electrons.
16. Define proton.
a. Positively charged particle found in the nucleus.
17. Define neutron.
a. Neutral particle found in the nucleus, same size as a proton.
18. Define electron.
a. Negatively charged particle found outside of the nucleus. 1/2000 size of proton.
19. Define fission.
a. Atom splits apart.
20. Define fusion.
a. Atoms fuse together.
21. Define half-life.
a. Time it take half a radioactive substance to decay.
22. Define alpha decay.
a. Helium-4 nucleus
23. Define beta decay.
a. Electron
24. Define gamma decay.
a. Energy
25. What material can block alpha decay?
a. Paper
26. What material can block beta decay?
a. Aluminum
27. What material can block gamma radiation?
Chemistry – HOMEWORK
a. Lead, concrete
28. Describe the plum pudding model of the atom.
a. Negative plums suspended in positive matrix.
29. Describe the planetary model of the atom.
a. Nucleus in center, electrons orbit outside.
30. Who conducted the gold foil experiment?
a. Rutherford
31. What was discovered in the gold foil experiment?
a. Nucleus
32. Who conducted the Cathode Ray Tube experiment?
a. JJ Thomson
33. What was discovered in the cathode ray tube experiment?
a. Electrons
34. What was discovered in the oil drop experiment?
a. Mass-charge ratio of electrons.
35. Who conducted the oil drop experiment?
a. Millikan
36. Who erroneously believed in the four elements Earth, Air, Fire, and Water?
a. Aristotle
37. How is John Dalton important in modern atomic theory?
a. 5 principles about reactions and identity of atoms, reintroduced concept of atoms
38. What is the mass number of Carbon-14
a. 14
39. What is the mass number of Helium-3?
a. 3
13
40. What is the mass number of
C
6
a. 13
41. What is the mass number of Calcium-42?
a. 42
42. What is the atomic mass of Iron
a. 55.847
43. What is the atomic mass of Calcium
a. 40.078
44. What is the atomic mass of Neon
a. 20.180
45. What is the atomic mass of Cobalt
a. 58.933
46. What is the atomic mass of methane, CH4
a. 16
47. What is the molar mass of Copper
a. 63.546
48. What is the molar mass of Magnesium
a. 24.305
49. What is the molar mass of Carbon Dioxide CO2
a. 44
50. What is the molar mass of Ammonia, NH3
a. 17.04
51. What is the molar mass of Copper chloride, CuCl2
a. 134.452
52. What is the molar mass of propane C3H8?
a. 44
53. How is atomic mass of an element calculated?
a. From the periodic table
54. How is the molar mass of a compound such as H2O or NaCl calculated?
a. Sum of individual atomic masses
Chemistry – HOMEWORK
55. How many particles are in one mole of a substance?
a. 6.02 x 1023
56. Explain how you convert from GRAMS to MOLES
a. Divide by the molar mass
57. Explain how you convert from MOLES to GRAMS
a. Multiply by the molar mass
58. What form of radioactive decay has the most penetrating power?
a. Gamma
59. Least, above?
a. Alpha
60. What is the formula for density?
a. Mass / volume
61. What is the formula for percent error?
a. Actual-experimental / Actual
Chemistry – HOMEWORK