Determine the frequency and energy of light with a wavelength of 899.7 nm

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# Determine the frequency and energy of light with a wavelength of 899.7 nm - PowerPoint PPT Presentation

Determine the frequency and energy of light with a wavelength of 899.7 nm. The Bohr Model of the Atom. I pictured electrons orbiting the nucleus much like planets orbiting the sun. But I was wrong! They’re more like bees around a hive. Neils Bohr. Quantum Mechanical Model of the Atom.

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## Determine the frequency and energy of light with a wavelength of 899.7 nm

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Presentation Transcript
The Bohr Model of the Atom

I pictured electrons orbiting the nucleus much like planets orbiting the sun.

But I was wrong! They’re more like bees around a hive.

Neils Bohr

Quantum MechanicalModel of the Atom

Mathematical laws can identify the regions outside of the nucleus where electrons are most likely to be found.

These laws are beyond the scope of this class…

Heisenberg Uncertainty Principle

“One cannot simultaneously determine both the position and momentum of an electron.”

You can find out where the electron is, but not where it is going.

OR…

You can find out where the electron is going, but not where it is!

Werner

Heisenberg

Electron Energy Level (Shell)

Generally symbolized by n, it denotes the probable distance of the electron from the nucleus. “n” is also known as the Principle Quantum number

Number of electrons that can fit in a shell:

2n2

Principal Quantum number
• Symbolized by letter n
• Indicates the main energy level occupied by the electron
• n can only be positive integers 1,2,. . .
• As n increases electron’s energy increases
• Total number of orbitals in a given level is = to n2

Electron Orbitals

An orbital is a region within an energy level where there is a probability of finding an electron.

Orbital shapes are defined as the surface that contains 90% of the total electron probability.

sOrbital shape

The s orbital has a spherical shape centered around

the origin of the three axes in space.

porbital shape

There are three dumbbell-shaped porbitals in each energy level above n = 1, each assigned to its own axis (x, y and z) in space.

Things get a bit more complicated with the five d orbitals that are found in the d sublevels beginning with n = 3. To remember the shapes, think of “double dumbells”

d orbital shapes

…and a “dumbell

with a donut”!

Electron Spin

Electron spin describes the behavior (direction of spin) of an electron within a magnetic field.

Possibilities for electron spin:

Pauli Exclusion Principle

Two electrons occupying the same orbital must have opposite spins

Wolfgang

Pauli

RULES GOVERNING e- CONFIGURATIONS
• Pauli exclusion principle- each orbital can hold TWO electrons with opposite spins
• Aufbauprinciple- an e- occupies the lowest-energy orbital first
• Hund’sRule- within a sublevel, place one e- per orbital before pairing them
• Empty bus seat rule!

Class A

Class C

Class D

Electron configuration pattern

1s

2s 2p

3s 3p 3d

4s 4p 4d 4f

5s 5p 5d 5f

6s 6p 6d 6f

7s 7p 7d 7f

Electron configuration pattern

1s

2s 2p

3s 3p 3d

4s 4p 4d 4f

5s 5p 5d 5f

6s 6p 6d 6f

7s 7p 7d 7f

Two types of notation for electrons
• Orbital Notation:
• an orbital is written as a line
• each orbital has a name written below it
• electrons are drawn as arrows (up and down)
• Electron Configuration Notation
• number of electrons in sublevel is added as a superscript 1s22s22p63s23p64s1

Silicon

• number of electrons: 14
• last electron is in sublevel: 3p

1s 2s 2p 3s 3p

• Valence Electrons- the electrons in the outermost energy level

Chlorine

1s 2s

• number of electrons: 17
• last electron is in sublevel: 3p

2p 3s 3p

Sodium

• number of electrons: 11
• last electron is in sublevel: 3s

1s2 2s2 2p63s1

1s 2s 2p 3s

Sodium

• number of electrons: 11
• last electron is in sublevel: 3s
• 3p1

1s2 2s2 2p63s1

1s 2s 2p 3s

Sodium

• number of electrons: 11
• last electron is in sublevel: 3s
• 3p1

1s2 2s2 2p63s1 3.189 x 10-19 J

what is the wavelength of light emitted?

1s 2s 2p 3s

Fluorescent Lamp

(metal vapor lamp)

• Mercury
• number of electrons: 80
• last electron is in sublevel: 5d

1s2 2s2 2p63s2 3s23p6 4s2 3d104p6 5s2

Fluorescent Lamp

(metal vapor lamp)

• Mercury
• number of electrons: 80
• last electron is in sublevel: 5d
• 5p1

1s2 2s2 2p63s2 3s23p6 4s2 3d104p6 5s2

7.423 x 10-19 J

what is the wavelength of light emitted?

Bromine

• number of electrons: 35
• last electron is in sublevel: 4p

1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5

1s 2s 2p 3s 3p

1s 2s 2p 3s 3p

4s 3d 4p

4s 3d 4p

Argon

• number of electrons: 18
• last electron is in sublevel: 3p

1s2 2s2 2p63s2 3p6

1s 2s 2p 3s 3p

Noble Gas Notation

• short hand for larger atoms
• configuration for the last noble gas is abbreviated by the noble gas’s symbol in brackets