Download The Atom

Timeline of Atomic Theory
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Make sure it has
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Dates (some may not have dates)
Important Peoples Names
What they found/discovered/believed to be true
The experiment they did
Picture of the model they developed (if there is
one)
The Atom
What is it made of???
Protons
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Positively charged
Mass = 1 amu = 1.67 x10-24 grams
Located in the nucleus
Gives an atoms its identity (atomic number)
Neutrons
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Neutral charge
Mass = 1 amu =1.67 x10-24 grams
Located in the nucleus
Different numbers of neutrons define isotopes
Electrons
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Negative charge
Mass = 1/1840 amu = 9.11 x10-28 grams
Located outside the nucleus (energy levels,
shells, orbitals)
Equal to the number of protons in a neutral
atom
Loss or gain of electrons gives ions their
charge
Isotopes
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The identity of the element depends on the
number of protons
Atoms of the same element can have different
number of neutrons.
Atoms of the same element that has different
number of neutrons have different masses.
Isotope Designation
Mass number
Atomic number
235
92
U
Element Symbol
*Nuclides of Hydrogen
1
1
H
2
1
H
3
1
H
More Isotope Designation
Plutonium-241
(Name of element- mass number)
# neutrons = Mass # - atomic #
They both have 6 protons.
Carbon-12
Carbon-14
6 neutrons
8 neutrons
Atomic Number
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Gives an atom its identity
# Protons
The whole number in bold type in each element
square (1)
17
35.453
Cl
Chlorine
Atomic Mass
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The mass average of all naturally occurring
isotopes of an element
The number expressed as a decimal in each
element square
11
22.990
Na
Sodium
Determination of Atomic Mass
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There are three isotopes of oxygen; and their relative
abundances:
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Oxygen -16
Oxygen-17
Oxygen-18
99.759 %
0.037 %
0.204 %
Lets figure out the atomic weight of oxygen together!
Mass Number
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Sum of the protons + neutrons
Always a whole number
Representation
Mass Number
12
C
6
Atomic Number
M
Symbol
A
X
Electron Energy Levels
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1 has a maximum of 2 electrons
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2 has a maximum of 8 electrons
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Both in the “s” sublevel
2 in the “s” sublevel
6 in the “p” sublevel
3 has a maximum of 18 electrons
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2 in the “s” sublevel
6 in the “p” sublevel
10 in the “d” sublevel
Electron Energy Levels (cont.)
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4 has a maximum of 32 electrons
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2 in the “s” sublevel
6 in the “p” sublevel
10 in the “d” sublevel
14 in the “f” sublevel
Electron Configurations
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Hydrogen – has only one electron in the first
energy level and the first sublevel
1
H: 1s
1
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Helium – has 2 electrons in the first energy
level filling it to capacity
2
He: 1s
2
Electron Configurations (cont.)
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Lithium – has 2 electrons in the first energy level
and one in the second
22s1
Li:
1s
3
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Be – has 2 e- in the first energy level and 2 in the
second but they both go into the “s” sublevel
4
Be: 1s22s2
Electron Configurations (cont.)
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Carbon – has 2 electrons in the first energy level and
four in the second
C: 1s22s22p2
6
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Fluorine – has 2 e- in the first energy level and 5 in
the second but they go into both the “s” & “p”
sublevels
F: 1s22s22p5
9
Rules for Orbital Diagrams for an
Atom
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Aufbau – electrons fill lowest energy levels
first ( follow the diagonal rule)
Pauli Exclusion Principle- There can only be
2 electrons in an orbital
Hund’s Rule – electrons fill equal energy
orbitals with one first before they pair
Orbital Diagram for A Nitrogen
Atom
N
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1s
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2s
2p
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3s
Orbital Diagram for A Fluorine
Atom
F
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1s
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2s
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2p
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
3s
Orbital Diagram for A Magnesium
Atom
Mg
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1s
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2s
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2p
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3s