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Chapter 3 Atoms and Elements

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Title: Chapter 3 Atoms and Elements


1
Chapter 3Atoms and Elements
  • The Atom
  • Atomic Number and Mass Number
  • Isotopes

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

3
Subatomic Particles
  • Particle Symbol Charge Relative
  • Mass
  • Electron e- 1- 0
  • Proton p 1
  • Neutron n 0 1

4
Location of Subatomic Particles
  • 10-13 cm
  • electrons
  • protons
  • neutrons
  • 10-8 cm

nucleus
5
Atomic Number
  • Counts the number
  • of
  • protons
  • in an atom

6
Atomic Number on the Periodic Table
  • 11
  • Na

Atomic Number
Symbol
7
(No Transcript)
8
All atoms of an element have the same number of
protons
  • 11
  • Na

11 protons
Sodium
9
Learning Check
  • 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

10
Solution
  • 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

11
Mass Number
  • Counts the number
  • of
  • protons and neutrons
  • in an atom

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

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
Subatomic Particles in Some Atoms
  • 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-

15
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

16
Learning Check
  • 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 _______ _______
    _______

17
Solution
  • 12C 13C 14C
  • 6 6
    6
  • p 6 6 6
  • n 6 7 8
  • e 6 6 6

18
Learning Check
  • 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

19
Solution
  • 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

20
Learning Check
  • 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- ___________

21
Solution
  • 16O
  • A. 8 p, 8 n, 8 e- 8
  • B. 17p, 20n, 17e- 37Cl
  • 17
  • C. 47p, 60 n, 47 e- 107Ag
  • 47

22
Why atoms get together to form compounds
  • Example Sodium has one valence electron and
    chlorine has seven.
  • Sodium wants to get rid of the one valence
    electron, then the remaining (new) outer energy
    level would have eight, and be filled (and
    happy)
  • If chlorine gains one, it will now have a full
    outer energy level and be happy too!

23
Sodium and Chlorine
-

11
17
11 and 10- 1 Na
17 and 18- 1- Cl-
Click to view animation
Click for another example
24
  • Magnesium has two valence electrons, and oxygen
    needs two so theyll form a compound in which
    magnesium gives away 2 electrons (giving it a 2
    charge) and oxygen gains the two electrons
    (giving oxygen a 2- charge)

25
Magnesium and Oxygen
2
2-
12
8
12 and 10- 2 Mg2
8 and 10- 2- O2-
Click for animation
Click for another example
26
  • Magnesium wants to give up 2 electrons, but
    remember that chlorine atoms only want to gain
    one electron in order to fill their outer energy
    levels. So if magnesium wants to get rid of both
    valence electrons, it needs to find two chlorine
    atoms.

27
Magnesium and Chlorine
-
-
2
17
12
17
17 and 18- 1- Cl-
17 and 18- 1- Cl-
12 and 10- 2 Mg2
Click to view animation
Click here to return to bonding options
28
Atomic Mass
  • Atomic mass is the weighted average mass of all
    the atomic masses of the isotopes of that atom.

29
Atomic Mass on the Periodic Table
  • 11
  • Na
  • 22.99

Atomic Number
Symbol
Atomic Mass
30
Example of an Average Atomic Mass
  • Cl-35 is about 75.5 and Cl-37 about 24.5 of
    natural chlorine.
  • 35 x 75.5 26.4
  • 100
  • 35.5
  • 37 x 24.5 9.07
  • 100

31
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