Atomic Theory and the Periodic Table Atomic Theory and the Periodic Table
Atomic Structure The Periodic Table, Isotopes, and Average Atomic Mass.
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Transcript of Atomic Structure The Periodic Table, Isotopes, and Average Atomic Mass.
Atomic Structure
The Periodic Table, Isotopes, and Average
Atomic Mass
Atomic Number
• Number of protons in an atom
• Periodic table is arranged by increasing atomic number
• The number of electrons in a neutral atom equals the number of protons in that atom
Reading the Periodic Table
H
Hydrogen
1
1.008
Element Name
Atomic Number
Symbol
Atomic Mass (amu)
Mass Number
• Sum of protons and neutrons in an atom
NOT THE SAME AS ATOMIC MASS!
H
Hydrogen
1
1.008
Cannot be found on periodic table
NO NO NO NO NO!!!!
6
CCarbon12.011
Atomic Number
ElementSymbol
ElementName
Atomic Massround this off
to get Mass Number
Reading the Periodic Table
Reading the Periodic Table
Number of:
Protons = Atomic Number
Neutrons = Mass Number – Atomic Number
Electrons = Atomic Number
Wrap-Up 1
• Which of the following can be found on a periodic table?
1) Atomic number
2) Atomic mass
3) Mass number
What’s in a cheeseburger?
Isotope• Atoms with same number of
protons, but different number of neutrons
HYDROGEN - 1 HYDROGEN - 2 HYDROGEN - 3
= neutrons
= protons
= electrons
3 Different Hydrogen Isotopes
HYDROGEN – 1(protium)
1 proton0 neutrons1 electron
HYDROGEN – 2(deuterium)
HYDROGEN – 3(tritium)
1 proton1 neutron1 electron
1 proton2 neutrons1 electron
Ways to Write Isotopes
1) Hyphen notation (2 parts)
name of element – # OR symbol – #
ex: carbon-14 OR C-14 chlorine-35OR Cl-35 hydrogen-3 OR H-3
MASSNUMBER
Ways to Write Isotopes
2) Nuclear symbol (3 parts)
C14
6
elementsymbol
mass number
atomic number
Ex problem
K
Potassium
19
39.10
# protons
# neutrons
# electrons
Nuclearsymbol
Potassium-39 Potassium-40 Potassium-41
19
19
1919
19
2220 21
19
K KK39
19
41
19
40
19
Wrap Up 2
• There are three common isotopes of carbon. The most prevalent has a mass of 12 amu. The other two have masses of 13 amu or 14 amu. Write the nuclear symbols for all three of these carbon isotopes.
CCC 146
136
126
Mass of Individual Atoms
• Atoms have extremely small masses (~1×10-27 kg)
• Instead we use a relative mass – atomic mass unit (amu)
• 1 amu ≈ mass of 1 proton or 1 neutron
Comparing Subatomic Particles
particle Mass (amu)
e-
p+
n0
0.000549
1.007276
1.008665
0
1
1
Atomic Mass
• Weighted average mass of all isotopes of an element
• Where can it be found found on periodic table?
K
Potassium
19
39.10
Example: calculate atomic mass of chlorine
Isotope mass (amu) percent abundance
35Cl 35 75.770%37Cl 37 24.230%
amu
amuamu
amuamu
485.35
965.8520.26
24230.03775770.035
decimal as %isotopeisotope of mass mass Atomic
Which isotope is most abundant?Ar-38, Ar-40, or Ar-41?
Ar
Argon
18
39.948
Ar-40