Transcript Bohr Model - Montgomery County Schools

Bohr Model
Lewis Structure
Bohr Model
• Introduced in 1913 by Niels Bohr
• Depicts the atom as a small, positively charged
nucleus surrounded by electrons.
• Why do we use the Bohr model?
– Simple and easy to understand
– Representation of subatomic particles
– Valence Electrons
How to Draw Bohr Diagrams
Bohr Diagrams
1) Find your element on the periodic table.
2) Determine the number of electrons – it is the
same as the atomic number.
3) This is how many electrons you will draw.
Bohr Diagrams
• Find out which period
(row) your element is in.
• Elements in the 1st
period have one energy
level.
• Elements in the 2nd
period have two energy
levels, and so on.
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Bohr Diagram
Energy Level
• 1
• 2
• 3
• 4
• 5
• 6
Electron Capacity
• 2
• 8
• 18
• 32
• 50
• 71
http://images.tutorvista.com/cms/ima
ges/81/different-energy-levels.png
Bohr Diagrams
P-6
N- 6
1) Draw a nucleus with
the p and n in the
nucleus.
2) Carbon is in the 2nd
period, so it has two
energy levels, or shells.
3) Draw the shells around
the nucleus.
4) Put how many protons
and neutrons in the
center
Bohr Diagrams
P- 6
N-6
1) Add the electrons.
2) Carbon has 6
electrons.
3) The first shell can only
hold 2 electrons.
Bohr Diagrams
P
N
1) Since you have 2
electrons already
drawn, you need to
add 4 more.
2) These go in the 2nd
shell.
3) Add one at a time starting on the right
side and going counter
clock-wise.
Bohr Diagrams
P
N
1) Check your work.
2) You should have 6 total
electrons for Carbon.
3) Only two electrons can
fit in the 1st shell.
4) The 2nd shell can hold up
to 8 electrons.
5) The 3rd shell can hold 18,
but the elements in the
first few periods only
use 8 electrons.
Bohr Diagrams
Try the following elements
on your own:
P
N
a)
b)
c)
d)
e)
f)
H
He
O
Al
Ne
K
Bohr Diagrams
Try the following elements
on your own:
H
a)
b)
c)
d)
e)
f)
H – 1 electron
He
O
Al
Ne
K
Bohr Diagrams
Try the following elements
on your own:
He
a)
b)
c)
d)
e)
f)
H
He - 2 electrons
O
Al
Ne
K
Bohr Diagrams
Try the following elements
on your own:
O
a)
b)
c)
d)
e)
f)
H
He
O - 8 electrons
Al
Ne
K
Bohr Diagrams
Try the following elements
on your own:
Al
a)
b)
c)
d)
e)
f)
H
He
O
Al - 13 electrons
Ne
K
Bohr Diagrams
Try the following elements
on your own:
Ne
a)
b)
c)
d)
e)
f)
H
He
O
Al
Ne - 10 electrons
K
Bohr Diagrams
Try the following
elements on your own:
K
a)
b)
c)
d)
e)
f)
H
He
O
Al
Ne
K - 19 electrons
Lewis Structure
• Electron-dot diagrams
• Represents paired and unpaired valence
electrons in an atom
• Covalent Bond- sharing electrons
• Valence Electron- electrons in the outer most
shell; electrons that are transferred or shared
when atoms bond together
How to Draw Lewis
Structures
Lewis Structures
1) Find your element on the periodic table.
2) Determine the number of valence electrons.
3) This is how many electrons you will draw.
Lewis Structures
• Find out which group
(column) your element is
in.
• This will tell you the
number of valence
electrons your element
has.
• You will only draw the
valence electrons.
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Groups - Review
Group 1 = 1 electron
Group 2 = 2 electrons
Group 8 = 8 electrons
Except for He, it has 2
electrons
•Each column is
called a “group”
•Each element in a
group has the same
number of electrons
in their outer orbital,
also known as
“shells”.
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•The electrons in the
outer shell are called
“valence electrons”
Lewis Structures
1) Write the element
symbol.
2) Carbon is in the 4th
group, so it has 4
valence electrons.
3) Starting at the right,
draw 4 electrons, or
dots, counterclockwise around the
element symbol.
Lewis Structures
1) Check your work.
2) Using your periodic
table, check that
Carbon is in the 4th
group.
3) You should have 4
total electrons, or
dots, drawn in for
Carbon.
Lewis Structures
On your worksheet, try
these elements on your own:
a)
b)
c)
d)
e)
f)
H
P
Ca
Ar
Cl
Al
Lewis Structures
On your worksheet, try
these elements on your own:
a)
b)
c)
d)
e)
f)
H
P
Ca
Ar
Cl
Al
Lewis Structures
On your worksheet, try
these elements on your own:
a)
b)
c)
d)
e)
f)
H
P
Ca
Ar
Cl
Al
Lewis Structures
On your worksheet, try
these elements on your own:
a)
b)
c)
d)
e)
f)
H
P
Ca
Ar
Cl
Al
Lewis Structures
On your worksheet, try
these elements on your own:
a)
b)
c)
d)
e)
f)
H
P
Ca
Ar
Cl
Al
Lewis Structures
On your worksheet, try
these elements on your own:
a)
b)
c)
d)
e)
f)
H
P
Ca
Ar
Cl
Al
Lewis Structures
On your worksheet, try
these elements on your own:
a)
b)
c)
d)
e)
f)
H
P
Ca
Ar
Cl
Al
Complete the Lewis Structure
Worksheet
You should know how to draw
Lewis Structures for the first
20 elements.
1. The Bohr Model was introduced
by which of the following scientists
A.
B.
C.
D.
Albert Einstein
Neils Bohr
Charles Darwin
Gregor Mendel
2. The Bohr model depicts
A. The atom as a small positively charged
nucleus surrounded by electrons.
B. Paired and unpaired valence electrons in an
atom.
C. Covalent bonds
D. Valence Electrons
3. In the periodic table, the rows
represent
A.
B.
C.
D.
Groups
Covalent Bonds
Ionic Bonds
Periods
4. In the periodic table, the
columns represent
A.
B.
C.
D.
Periods
Covalent Bonds
Groups
Ionic Bonds
5. The Lewis Structure represents
A. Paired and unpaired valence electrons in an
atom.
B. The atom as a small positively charged
nucleus surrounded by electrons.
C. Valence Electrons
6. When drawing a Bohr model,
how do you determine the number
of electrons?
A.
B.
C.
D.
Valence Electrons
Mass Number
Atomic Number
Atomic Mass Unit
7. When drawing a Lewis Structure,
how do you determine the number
of valence electrons?
A.
B.
C.
D.
Atomic Number
Mass Number
Atomic Mass Unit
By looking at the column the element is
found in
8. The Lewis Structure is also
known as
A.
B.
C.
D.
Bohr Model
The electron dot diagram
Valence Electrons
The planetary model
9. When drawing a Lewis Structure,
in which direction do you move
when drawing the dots?
A.
B.
C.
D.
Counter-clockwise around the element
Clockwise around the element
North
Southwest
10. When drawing a Bohr model,
how do you determine the number
of energy levels to use?
A.
B.
C.
D.
Groups
Columns
Periods
Atomic Number
[Default]
[MC Any]
[MC All]