Atoms

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Atoms Isotopes NOTES
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Reading the Periodic Table
A E M
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Reading Atoms Isotopes
Or
Element Name M
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Atomic Number

• The number of Protons in the nucleus of a given
  atom
• Remember All atoms as a whole want to have a
  Neutral electrical charge.
  
  
  
  
  
  
  
  
  

Atomic
the of Protons


the of electrons
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Mass Number

• The sum of the number of protons and number of
  neutrons in the nucleus of an atom.
• Example

6 p
6 n
Carbon - 12
12
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Isotopes

• Atoms that have the same number of Protons but
  different numbers of Neutrons.
• Example

Bromine - 79
35p and 44n
Bromine - 80
35p and 45n
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Average Atomic Mass

• The average mass of all isotopes of an element.
• Example
• In a sample of 100 Carbon atoms
• 99 of them are Carbon-12
• 1 is a Carbon-14.

Whats the Average Atomic Mass?
12.02
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Finding the of Neutrons

• Use the formula below

of Neutrons Mass - Atomic
3 Li 6.94
Lithium
3
3
4
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Unit of Measurement (MASS)

• Atomic Mass Unit (amu)
• one-twelfth the mass of a carbon-12 atom. (6P
  6N)
• 1 amu 1.665402 x 10-27 Kg
• 1p 1.007280 amu
• 1n 1.008670 amu
• 1e 0.000549 amu

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Practice Problems
50 Sn 118.71

• Element _________ Symbol _________
• Protons _________ Protons ________
• Electrons _________ Electrons ________
• Neutrons _________ Neutrons ________

Magnesium-24
Tin
Mg
50
12
50
12
12
69
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More Practice Problems

• Element _________ Element _________
• Protons _________ Protons ________
• Electrons _________ Electrons ________
• Neutrons _________ Neutrons ________

Chromium
Gold
24
79
79
24
28
118
12
More Practice Problems

• Element _________ Element _________
• Protons _________ Protons ________
• Electrons _________ Electrons ________
• Neutrons _________ Neutrons ________

Chlorine
Chlorine
17
17
17
17
18
20