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Do Now
Where are the electrons found in the Rutherford model of the atom?
Revolving around the nucleus
Why don’t they fall into the positively charged nucleus?
Centripetal force
Can the distance between the nucleus and an electron change?

2. Bohr Model of the Atom

3. Bohr Observations
When solutions containing metal ions are heated, they give off characteristic colors.
What does this mean?
Bohr related the color of light to the electrons in an atom.
Sodium
Potassium
Calcium
Barium

4. Bohr’s Model of the Atom
Electrons move around the nucleus like planets around the sun.
In specific circular paths, or energy levels, different distances from the nucleus.
An amount of fixed energy separates one level from another.
When electrons fall to lower energy levels they release a certain color of light

5. The Bohr Model of the Atom
I pictured the electrons orbiting the nucleus much like planets orbiting the sun.
However, electrons are found in specific circular paths around the nucleus, and can jump from one level to another.
Neils Bohr

6. Bohr’s model Energy levels of an atom like the rungs of a ladder
The electron cannot exist between energy levels, just like you can’t stand between rungs on a ladder
Electrons can absorb energy and move to a higher energy level
The higher the energy level, the more unstable the electron
Unstable electrons fall to lower energy levels and release light

7. } Bohr’s Model Further away from the nucleus means more energy.
There is no “in between” energy
High energy electrons are unstable and eventually fall to a lower energy level releasing light along the way
Fifth
Fourth
Increasing energy
Third
Second
First
Nucleus

8. Principal Quantum Number
Principal quantum number (n) denotes the shell (energy level) in which the electron is located.
Maximum number of electrons that can fit in an energy level:
2n2

9. Principal Quantum Number
Determining the maximum # of electrons in an energy level.
# of electrons = 2n2
Eg. n=1 2(1)2=2
n=2 2(2)2=8
n= (3)2=18

10. Changing Energy Levels
Let’s look at a hydrogen atom

11. Changing Energy Levels
Heat, electricity, or light can move the electron up energy levels

12. Changing Energy Levels
As the electron falls back to ground state it gives the energy back as light

13. Changing Energy Levels
May fall down in steps
Each with a different energy

14. The Bohr Ring Atom
n = 4
n = 3
n = 2
n = 1

15. Regents Practice