Download Atomic Structure Notes

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September 20, 2012
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Untitled.notebook
September 20, 2012
Modern Atomic Theory
• All matter is composed of atoms
• Atoms cannot be subdivided, created, or
destroyed in ordinary chemical reactions. However,
these changes CAN occur in nuclear reactions!
• Atoms of an element have a characteristic
average mass which is unique to that element.
• Atoms of any one element differ in
properties from atoms of another element.
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September 20, 2012
Rutherford‐Bohr Model
‐ neutrons and protons occupy a dense central region called the nucleus
‐ electrons orbit the nucleus
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Parcle Charge Mass # Locaon Neutron 0 1 Nucleus Proton +1 1 Nucleus Electron ‐1 0 Electron Cloud 4
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September 20, 2012
Atomic number (Z) of an element is the
number of protons in the nucleus of each
atom of that element.
Element # of Protons
Atomic # (Z)
Carbon 6 6 Phosphorus 15 15 Gold 79 79 5
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September 20, 2012
Mass number is the number of protons
and neutrons # electrons= #protons
Mass # = p + + n o
Element Mass Protons Electrons Neutrons
Oxygen 8 42 6
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Isotopes are atoms of the same
element having different masses due
to varying numbers of neutrons.
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An ion is an atom or molecule that
has a positive or negative charge
Cl + e- -> Cl -
Al -> Al
+
+ e-
Cl- has an extra electron
therefore it has a negative
charge
Al+ is missing an electron so
it has a positive charge
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Element
September 20, 2012
Mass #
Atomic # # protons # electron # neutrons 1
3
9
13
potassium
40
29
36
55
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