Electron Configuration

Radiant Energy

Waves

• Light travels as both Waves and Packets of energy.

• Light is a form of Electromagnetic Radiation.– EM Radiation has

waves in the electric and magnetic fields

• All waves (Water or Electromagnetic) have 4 key characteristics:– Amplitude

– Wavelength

– Frequency

– Speed

Wave Characteristics

• Amplitude.– Height of a wave from

origin to a peak/crest.

– Affects brightness and intensity.

• Wavelength.– Distance from crest to crest.

Distance for one full cycle.

– Visible light: 400-750nm.

Wave Characteristics

• Frequency.– How fast a wave oscillates

(moves up and down).

– Units: s-1, 1/s or Hz.

• Speed.– Speed of light a constant:

3.00 X 108 m/s.

• Frequency and Wavelength related by the equation: = c /

Try this…

If the frequency of a wave is 93.1 x 106 s-1, what is the wavelength?

Answer: 3.22 m

If the wavelength of a wave is 1.54 mm, what is it’s frequency?

Answer: 1.95 x 1011 Hz (s-1)

Have a Problem?

Rearranging the equation:

• First, multiply by (frequency): = (c/)

• Now, divide by (wavelength):() / = c /

• Leaving: = c/Moving on….

Electromagnetic Spectrum

• Many parts including:– Gamma Rays (10-11 m)

– X-Rays (10-9 m)

– Ultra-violet (10-8 m)

– Visible (10-7 m)

– Infared (10-6 m)

– Microwave (10-2 m)

– TV/Radio (10-1 m)

Electromagnetic Spectrum

• Visible Spectrum:ROY G BIV

– Red

– Orange

– Yellow

– Green

– Blue

– Indigo

– Violet

Electromagnetic Spectrum (once more)

Electron Configuration

Quantum Theory

Early Puzzlements

• Wave model for light was originally accepted by scientific community.

• This couldn’t explain why metals heating first emitted invisible radiation and then visible radiation.

• Other questions included why elements only emitted certain characteristic colors of light.

Plank’s Theory

• Every object can only absorb or emit a fundamental amount of energy.

• This amount is called a quantum.

• The amount is like moving up or down steps.

Plank’s Theory

• Plank’s Theory is based on the relationship between frequency and the energy of the particle.

• E = h• Plank’s Constant:

– h = 6.6262 X 10-34 J-s

Quick Practice

If a wave has a frequency of 9.33x106 Hz, what is it’s energy?

6.18x10-27 J

What is the frequency of a wave if its energy is 4.32x10-31 J?

652 Hz

Photoelectric Effect

• Einstein used Plank’s equation to explain a puzzling phenomenon, the Photoelectric Effect.– Electrons ejected from metal when light shines on it.

– Metal need’s certain frequency of light to release electrons. In Sodium, red light is no good, violet releases them off easily.

– Photons: Tiny particles of light providing energy to “knock off” electrons.

Dual Nature of Radiant Energy

• Proven in 1923 by Arthur Compton– Showed photon could

collide with an electron like tiny balls.

• Summary:– Light behaves as a

wave ( = c/)– Light behaves as a

particle (E = h)

Electron Configuration

Another Look at the Atom

Line Spectra

• Def: A spectrum that contains only certain colors/wavelengths.

• AKA: The Atomic Emission Spectrum

• Each element has it’s own “fingerprint” emission spectrum.

The Bohr Model

• Bohr drew the connection between Rutherford's model of the atom and Planks idea of quantization.

• Energy levels labeled with Quantum Numbers (n)

• Ground state, or lowest energy level – n=1

• Excited State – level of higher energy

Matter Waves

• If energy has dual nature, why not matter?• De Broglie thought so.

– Matter Waves – the wavelike behavior of waves.

– Didn’t stand without experimental proof

• Davison and Germer proved this with experiments in 1927.

• Why don’t we see these matter waves? Mass must be very small to observe wavelength.

Heisenberg Uncertainty

• Uncertainty Principle– The position and momentum of a moving

object cannot simultaneously be measured and known exactly.

• Translation:– Cannot know exactly where and how fast an

electron is moving at the same time.

Electron Configurations

A New Approach to the Atom

Quantum-mechanics Model

• Includes all the ideas of the atom we have covered:– Energy of electrons is quantized– Electrons exhibit wavelike behavior– Electrons position and momentum cannot be

simultaneously known– Model does describe the probable location of

electrons around the nucleus

Probability and Orbitals

• Electron Density:– The density of an

electron cloud.

• Atomic Orbitals:– A region around the

nucleus of an atom where an electron with a given energy is likely to be found.

• Kinds of orbitals:– Each kind has own

different basic shape.– Given letter

designations of s, p, d and f.

– s-orbitals are spherical– p-orbitals are dumbbell– d- and f-orbitals more

complex.

Orbitlas and Energy

• Principle energy levels (n) can be divided into sublevels.

• Number of sublevels is equal to the number of the principle energy level.

Orbitals and Energy

• Each sublevel has one or more orbitals– s – one

– P – three

– d – five

– f – seven

• Summary provided in figure 4-28 (pg 145)

Electron Spin

• Electrons have two spins:– Up or clockwise– Down or counterclockwise

• Only two electrons (one of each spin) can occupy an orbital. These electrons are said to be “paired”.

Electron Configurations

Electron Configurations