1. The Atom: Atomic Number , Mass Number and Isotopes
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2. 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. Subatomic Particles
Particle Symbol Charge Relative Mass Electron e Proton p+ 1+ 1amu Neutron n 0 1amu
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4. Location of Subatomic Particles
10-13 cm
electrons
protons
neutrons
10-8 cm
nucleus
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5. Counts the number of protons in an atom
Atomic Number (Z)
Counts the number of protons in an atom
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6. Atomic Number on the Periodic Table11 Na
Atomic Number
Symbol
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7. All atoms of an element have the same number of protons11 Na
11 protons
Sodium
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8. Learning Check AT 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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9. Solution AT 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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10. Number of Electrons An atom is neutral The net charge is zero
Number of protons = Number of electrons
Atomic number = Number of electrons
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11. Counts the number of protons and neutrons in an atom
Mass Number (A)
Counts the number of protons and neutrons in an atom
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12. Atomic Symbols Show the mass number and atomic number
Give the symbol of the element
mass number
23 Na sodium-23
atomic number 11
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13. More Atomic Symbols 16 31 65 8 15 30 O P Zn 8 p+ 15 p+ 30 p+
O P Zn
8 p p p+
8 n n n
8 e e e-
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14. 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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15. Learning Check AT 2 6 6 6 #P _______ _______ _______
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 14C
#P _______ _______ _______
#N _______ _______ _______
#E _______ _______ _______
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16. Solution AT 2 6 6 6 #P __6___ _ 6___ ___6___ #N __6___ _ _7___ ___8___
12C C 14C
#P __6___ _ 6___ ___6___
#N __6___ _ _7___ ___8___
#E __6___ _ 6___ ___6___
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17. Learning Check AT 3
An atom of zinc has a mass number of 65. A. Number of protons in the zinc atom 1) 30 2) 35 3) 65 B. Number of neutrons in the zinc atom C. What is the mass number of a zinc isotope with 37 neutrons? 1) 37 2) 65 3) 67
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18. Solution AT 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? 3) 67
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19. Learning Check AT 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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20. Solution AT 4 B. 17p+, 20n, 17e- 37Cl 17 47 16O A. 8 p+, 8 n, 8 e- 8
C. 47p+, 60 n, 47 e- 107Ag 47
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21. Learning Check AT 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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22. Solution AT 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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23. 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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24. Na 22.99 Atomic Mass Listed on the periodic table
Gives the mass of “average” atom of each element compared to 12C
Average atom based on all the isotopes and their abundance %
Atomic mass is not a whole number
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25. Learning Check AT6
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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26. Solution AT6
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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27. Atomic Mass of Magnesium
Isotopes Mass of Isotope Abundance
24Mg = 24.0 amu %
25Mg = amu %
26Mg = amu %
Atomic mass (average mass) Mg = 24.3 amu Mg
24.3
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