1. Unit 4: The Atom, And Isotopes
#5 PPT
APE MAN AND ISOTOPES!
Unit 4: The Atom,
Atomic Number, Mass Number,
And Isotopes
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2. LecturePLUS Timberlake
Atomic Theory
Atoms are building blocks of elements
Similar atoms in each element
Different from atoms of other elements
Two or more different atoms bond in simple ratios to form compounds
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3. LecturePLUS Timberlake
Subatomic Particles
Particle Symbol Charge Relative
Mass
Electron e
Proton p
Neutron n
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4. Location of Subatomic Particles
electrons
protons
neutrons
nucleus
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5. LecturePLUS Timberlake
Atomic Number
Counts the number of
protons (+)
in an atom
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6. LecturePLUS Timberlake
Periodic Table
Represents physical and chemical behavior of elements
Arranges elements by increasing atomic number
Repeats similar properties in columns known as chemical families or groups
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7. LecturePLUS Timberlake
Periodic Table 11 Na
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8. Atomic Number on the Periodic Table11 Na
Atomic Number
Symbol
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9. All atoms of an element have the same number of protons11 Na
11 protons
Sodium
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10. LecturePLUS Timberlake
Learning Check 1
State the number of protons for atoms of each of the following:
A. Nitrogen
1) 5 protons 2) 7 protons 3) 14 protons
B. Sulfur
1) 32 protons 2) 16 protons 3) 6 protons
C. Barium
1) 137 protons 2) 81 protons 3) 56 protons
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11. LecturePLUS Timberlake
Solution 1
State the number of protons for atoms of each of the following:
A. Nitrogen
2) 7 protons
B. Sulfur
2) 16 protons
C. Barium
3) 56 protons
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12. LecturePLUS Timberlake
Number of Electrons
An atom is neutral
The net charge is zero
Number of protons = Number of electrons
Atomic number = Number of electrons
APE! A=P=E
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13. protons (Atomic number) and neutrons
Mass Number
Counts the number of
protons (Atomic number) and neutrons
in an atom
MAN!
M=A+N or
M-A=N
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14. LecturePLUS Timberlake
Atomic Symbols
Show the mass number and atomic number
Give the symbol of the element
mass number Name:
23 Na sodium-23
atomic number 11
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15. LecturePLUS Timberlake
More Atomic Symbols
O P Zn
8 p p+ 30 p+
8 n 16 n 35 n
8 e e e-
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16. LecturePLUS Timberlake
Isotopes
Atoms with the same number of protons, but different numbers of neutrons.
Atoms of the same element (same atomic number) with different mass numbers
Isotopes of chlorine
35Cl 37Cl
chlorine chlorine - 37
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17. C Mass # Atomic # Isotopes 12 6 Nuclear symbol:
Atoms of the same element with different mass numbers. 12 6 C
Nuclear symbol:
Mass #
Each isotope has a different number of neutrons.
Atomic #
Hyphen notation: carbon-12 17
Courtesy Christy Johannesson 17

18. Isotopes 18 + + Carbon-12 Neutrons 6 Protons 6 Electrons6 Carbon-14
Nucleus
Neutron
Proton +
Electrons
Nucleus
Nucleus
Neutron
Proton +
Carbon-12
Neutrons 6
Protons 6
Electrons6
Electrons
The chemistry of each element is determined by its number of protons and electrons.
In a neutral atom, the number of electrons equals the number of protons.
Symbols for elements are derived directly from the element’s name.
Nuclei of atoms contain neutrons as well as protons.
The number of neutrons is not fixed for most elements, unlike protons.
Atoms that have the same number of protons, and hence the same atomic number, but different numbers of neutrons are called isotopes.
Carbon-14
Neutrons 8
Protons 6
Electrons6
Nucleus 18 18

19. 6Li 7Li 3 p+ 3 p+ 2e– 1e– 2e– 1e– 4 n0 3 n0 + + 19 Lithium-6 Lithium-7
Nucleus
Neutron
Proton
Nucleus
Neutron
Proton +
Electrons
Nucleus
Electrons +
Nucleus
Lithium-6
Lithium-7
Neutrons 3
Protons 3
Electrons 3
Neutrons 4
Protons 3
Electrons 3 19 19

20. Cl Isotopes Cl Chlorine-37 20 atomic #: 17 mass #: 37 # of protons: 17
# of electrons: 17
# of neutrons: 37 17 Cl
Atoms that have the same number of protons, and hence the same atomic number, but different numbers of neutrons are called isotopes. 20 20

21. Isotopes C-12 vs. C-14 Dalton was wrong.
Atoms of the same element can have different numbers of neutrons
different mass numbers
called isotopes
protons remain same
The word isotope comes from the Greek words isos, meaning "equal," and topos, meaning "place."
C vs. C-14 21
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22. Naming Isotopes Put the mass number after the name of the element 22
carbon- 12
carbon -14
uranium-235 22
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23. LecturePLUS Timberlake
Learning Check 2
Naturally occurring carbon consists of three isotopes, 12C, 13C, and 14C. State the number of protons, neutrons, and electrons in each of these carbon atoms.
12C C C
A. #P _______ _______ _______
B. #N _______ _______ _______
C. #E _______ _______ _______
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24. LecturePLUS Timberlake
Solution 2
12C C 14C
A. #P __6___ _ 6___ ___6___
B. #N __6___ _ _7___ ___8___
C. #E __6___ _ 6___ ___6___
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25. LecturePLUS Timberlake
Learning Check 3
An atom of zinc has a mass number of 65.
A. Number of protons in the zinc atom
1) ) ) 65
B. Number of neutrons in the zinc atom
C. What is the mass number of a zinc isotope
with 37 neutrons?
1) ) ) 67
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26. LecturePLUS Timberlake
Solution 3
An atom of zinc has a mass number of 65.
A. Number of protons in the zinc atom
1) 30
B. Number of neutrons in the zinc atom
2) 35
C. What is the mass number of a zinc isotope
with 37 neutrons? (MAN! M=A+N M= 30+37)
3) 67
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27. LecturePLUS Timberlake
Learning Check 4
Write the atomic symbols for atoms with the following:
A. 8 p+, 8 n, 8 e- ___________
B. 17p+, 20n, 17e- ___________
C. 47p+, 60 n, 47 e- ___________
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28. LecturePLUS Timberlake
Solution 4
16O
A. 8 p+, 8 n, 8 e
B. 17p+, 20n, 17e- 37Cl 17
C. 47p+, 60 n, 47 e- 107Ag 47
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29. LecturePLUS Timberlake
Learning Check 5
An atom has 14 protons and 20 neutrons.
A. Its atomic number is
1) ) ) 34
B. Its mass number is
C. The element is
1) Si 2) Ca 3) Se
D. Another isotope of this element is
1) 34X 2) 34X 3) 36X
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30. LecturePLUS Timberlake
Solution 5
An atom has 14 protons and 20 neutrons.
A. It has atomic number
1) 14
B. It has a mass number of
3) 34
C. The element is
1) Si
D. Another isotope of this element would be
3) 36X 14
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31. LecturePLUS Timberlake
Masses of Atoms
A scale designed for atoms gives their small atomic masses in atomic mass units (amu)
An atom of 12C was assigned an exact mass of amu
Relative masses of all other atoms was determined by comparing each to the mass of 12C
An atom twice as heavy has a mass of amu. An atom half as heavy is 6.00 amu.
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32. LecturePLUS Timberlake
Atomic Mass Na
22.99
Listed on the periodic table
Gives the mass of “average” atom of each element compared to 12C
Weighted Average is based on all the isotopes and their abundance %
Atomic mass is not a whole number
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33. LecturePLUS Timberlake
Learning Check 6
Using the periodic table, specify the atomic mass of each element (round to the tenths place):
A. calcium __________
B. aluminum __________
C. lead __________
D. barium __________
E. iron __________
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34. LecturePLUS Timberlake
Solution 6
Using the periodic table, specify the atomic mass of each element (round to the tenths place):
A. calcium _40.1 amu _
B. aluminum _27.0 amu _
C. lead _207.2 amu_
D. barium _137.3 amu_
E. iron _55.8 amu__
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35. Calculating Atomic Mass
Percent(%) abundance of isotopes
Mass of each isotope of that element
Weighted average =
mass isotope1(%) + mass isotope2(%) + …
Weighted Average = (Mass#)(%) + (Mass#)(%) +...
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36. Atomic Mass of Magnesium
Isotopes Mass of Isotope Abundance
24Mg = 24.0 amu x 78.70%
25Mg = amu x %
26Mg = amu x 11.17%
(then add)
Atomic mass (average mass) Mg = 24.3 amu Mg
24.3
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37. LecturePLUS Timberlake
Learning Check 7
Gallium is a metallic element found in small lasers used in compact disc players. In a sample of gallium, there is 60.2% of gallium-69 atoms and 39.8% of gallium-71 atoms. What is the atomic mass of gallium?
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38. LecturePLUS Timberlake
Solution 7
Ga-69
69 amu x = amu for 69Ga
100
Ga-71
71 amu x = amu for 71Ga
ADD!
Atomic mass Ga = amu
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