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The Atom

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The Atom Atomic Number and Mass Number Isotopes LecturePLUS Timberlake * LecturePLUS Timberlake * Finding An Isotopic Mass A sample of boron consists of 10B (mass 10 ... – PowerPoint PPT presentation

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Title: The Atom


1
  • The Atom
  • Atomic Number and Mass Number
  • Isotopes

2
Atoms, Elements, Subatomic Particles
  • Atoms The basic unit of a chemical element.
  • Elements each of more than one hundred
    substances that cannot be chemically
    inter-converted or broken down into simpler
    substances and are primary constituents of
    matter.
  • Subatomic Particles A particle smaller than an
    atom.

3
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

4
Subatomic Particles
  • Particle Symbol Charge Relative
  • Mass
  • Electron e- 1- 0
  • Proton p 1
  • Neutron n 0 1

5
Location of Subatomic Particles
  • 10-13 cm
  • electrons
  • protons
  • neutrons
  • 10-8 cm

nucleus
6
Atomic Number
  • Counts the number
  • of
  • protons
  • in an atom

7
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

8
Periodic Table
  • 1 2 3 4 5 6 7 8


11 Na
9
Atomic Number on the Periodic Table
  • 11
  • Na

Atomic Number
Symbol
10
All atoms of an element have the same number of
protons
  • 11
  • Na

11 protons
Sodium
11
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

12
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

13
Number of Electrons
  • An atom is neutral
  • The net charge is zero
  • Number of protons Number of electrons
  • Atomic number Number of electrons

14
Mass Number
  • Counts the number
  • of
  • protons and neutrons
  • in an atom

15
Atomic Symbols
  • Show the mass number and atomic number
  • Give the symbol of the element
  • mass number
  • 23 Na sodium-23
  • atomic number 11

16
More Atomic Symbols
  • 16 31 65
  • O P Zn
  • 8 15 30
  • 8 p 15 p 30 p
  • 8 n 16 n 35 n
  • 8 e- 15 e- 30 e-

17
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
  • 17 17
  • chlorine - 35 chlorine - 37

18
Learning Check AT 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 13C 14C
  • 6 6
    6
  • P _______ _______
    _______
  • N _______ _______
    _______
  • E _______ _______
    _______

19
Solution AT 2
  • 12C 13C 14C
  • 6 6
    6
  • P __6___ _ 6___
    ___6___
  • N __6___ _ _7___
    ___8___
  • E __6___ _ 6___
    ___6___

20
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
  • 1) 30 2) 35 3) 65
  • C. What is the mass number of a zinc isotope
  • with 37 neutrons?
  • 1) 37 2) 65 3) 67

21
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

22
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- ___________

23
Solution AT 4
  • 16O
  • A. 8 p, 8 n, 8 e- 8
  • B. 17p, 20n, 17e- 37Cl
  • 17
  • C. 47p, 60 n, 47 e- 107Ag
  • 47

24
Learning Check AT 5
  • An atom has 14 protons and 20 neutrons.
  • A. Its atomic number is
  • 1) 14 2) 16 3) 34
  • B. Its mass number is
  • 1) 14 2) 16 3) 34
  • C. The element is
  • 1) Si 2) Ca 3) Se
  • D. Another isotope of this element is
  • 1) 34X 2) 34X 3) 36X
  • 16 14
    14

25
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

26
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
    12.00 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 24.00 amu.
    An atom half as heavy is 6.00 amu.

27
Atomic Mass
Na 22.99
  • 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

28
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 __________

29
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__

30
Calculating Atomic Mass
  • Percent() abundance of isotopes
  • Mass of each isotope of that element
  • Weighted average
  • mass isotope1() mass isotope2()
  • 100 100

31
Atomic Mass of Magnesium
  • Isotopes Mass of Isotope Abundance
  • 24Mg 24.0 amu 78.70
  • 25Mg 25.0 amu 10.13
  • 26Mg 26.0 amu 11.17
  • Atomic mass (average mass) Mg 24.3 amu

Mg 24.3
32
Learning Check AT7
  • 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 (68.9
    amu) atoms and 39.8 of gallium-71 (70.9 amu)
    atoms. What is the atomic mass of gallium?

33
Solution AT7
  • Ga-69
  • 68.9 amu x 60.2 41.5 amu for 69Ga
  • 100
  • Ga-71 (/100)
  • 70.9 amu x 39.8 28.2 amu for 71Ga
  • 100
  • Atomic mass Ga 69.7 amu

34
Finding An Isotopic Mass
  • A sample of boron consists of 10B (mass 10.0
    amu) and 11B (mass 11.0 amu). If the average
    atomic mass of B is 10.8 amu, what is the
    abundance of each boron isotope?

35
  • Assign X and Y values
  • X 10B Y 11B
  • Determine Y in terms of X
  • X Y 100
  • Y 100 - X
  • Solve for X
  • X (10.0) (100 - X )(11.0) 10.8
  • 100 100
  • Multiply through by 100
  • 10.0 X 1100 - 11.0X 1080

36
  • Collect X terms
  • 10.0 X - 11.0 X 1080 - 1100
  • - 1.0 X -20
  • X -20 20 10B
  • - 1.0
  • Y 100 - X
  • 11B 100 - 20 80 11B

37
Learning Check AT8
  • Copper has two isotopes 63Cu (62.9 amu) and 65Cu
    (64.9 amu). What is the abundance of each
    isotope? (Hint Check periodic table for atomic
    mass)
  • 1) 30 2) 70 3) 100

38
Solution AT8
  • 2) 70
  • Solution
  • 62.9X 6490 64.9X 6350
  • -2.0 X -140
  • X 70
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