ELECTROMAGNETIC RADIATION

Form of energy Has a wave-like behavior. Travels through a vacuum (space) Moves at the speed of light (c = 3.00 x

108 m/s)WAVELENGTH (λ = lambda)Distance between two peaks on wave.

Measured in METERS

FREQUENCY (ν or nu)

# of waves that pass a given point per secondMeasured in Hertz (hz) or 1/s or s-1

c = λν Microwaves are used to transmit

information. What is the wavelength of a microwave having a frequency of 3.44 x 109 Hz?

An X-ray has a wavelength of 1.15 x 10-

10 m. What is its frequency?

c = λν

MAX PLANCK (1900) German Physicist Studied the light emitted from heated

objects.

Conclusion: Matter can gain or lose energy in small, specific amounts called quanta.

CHILD’s Blocks Analogy

Matter can only have certain amounts of energy released or absorbed (quanta).Cannot absorb or release quantities in between.

What is the energy of a photon from the violet portion of a rainbow if its frequency is 7.23 x 1014 Hz?

What is the energy of a photon of UV radiation that has a wavelength of 315 nm.

Hint: 1.0 m = 1.0 x 109 nm

c = λν

What is the wavelength of a wave with the frequency of 1 x 104 Hz ?

What is the energy associated with a wave with a frequency of 1 x 104 Hz?

c = λν

ALBERT EINSTEIN(1879 – 1955)

Fact: 1895 FAILED entry

exam to electrical engineering school

Jewish: Fled from Nazis in 1932

1905 Electromagnetic radiation has both wave-like and particle-like properties

THE PHOTOELECTRIC EFFECT

Definition: When light (photon) hits the surface of a metal with a HIGH enough frequency, electrons are emitted

Given 1921 Nobel Prize in Physics

NIELS BOHR(1885 -1962)

Teacher: J.J. Thomson Later studied with Ernest

Rutherford

• Electrons are found in energy levels around the nucleus.• Levels further from nucleus = greater energy

THE BOHR ATOM

Ground State – lowest allowable energy state of atom.

Gains energy, excited to higher energy level (excited state)

Emits energy (photon), as it falls back to the ground state.

Bohr’s model explained hydrogen’s observed spectral lines.

*PROBLEM: Failed to explain the spectrum of any other element.

LOUIS DE BROGLIE(1892 – 1987)

Radical Idea: “If light behaved as a wave or a particle, then why could not a particle, like an electron, behave like a wave?”

1st to theorized this idea (1929)

WERNER HEISENBERG(1901 – 1976)1927: “Heisenberg’s

Uncertainty Principle”

One cannot determine the POSITION and VELOCITY of an electron at the same time.

BALLOON IN DARK ROOM ANALOGY

QUANTUM MECHANICS The Heisenberg Uncertainty Principle

5.3

ERWIN SCHRÖDINGER(1887 – 1961)

Wave EquationTreats ELECTRONS as a wave

Calculates the 90% probability region where the ELECTRON is most likely to be found

A.K.A.: “Orbital”

THE QUANTUM MECHANICAL MODEL

The propeller blade has the same probability of being anywhere in the blurry region, but you cannot tell its location at any instant. The electron cloud of an atom can be compared to a spinning airplane propeller.

5.1

ORBITALS

• Results of the Schrödinger Wave Equation:

•90% probability region where an electron is most likely to be found around the nucleus.

QUANTUM MECHANICAL MODEL OF THE ATOM

Principal Energy Level (n)Indicates the relative size

and energies of orbitals.

Each principal energy level is divided into sublevels:

n=1 _____sublevel ( n=2 _____sublevels ( n=3 _____sublevels ( n=4 _____sublevels (

QUANTUM MECHANICAL MODEL OF THE ATOM

ORBITALSEach sublevel contains a number of orbitals.

Sublevel # orbitals Shapes Sphericalp Dumbbell d multiple lobesf Complex

Shapes

Different atomic orbitals are denoted by letters. The s-orbitals are spherical, and p-orbitals are dumbbell-shaped.

1s orbital vs. 2s orbital?How are the p-orbitals different?

ATOMIC ORBITALS

Four of the five d-orbitals have the same shape but different orientations in space.

ELECTRON CONFIGURATIONS

1. Aufbau Principle: Each electron occupies the lowest energy orbital available.

German for “Building up.”

2.

An orbital can only contain two electrons with opposite spins!

3.Hund’s Rule: must fill in each equal energy orbital before adding opposite spins.

Draw the orbital diagram for the following:H

He

Li

B

N

Na

DIAGONAL RULE MAKE A FLASH CARD WITH THIS ON IT.

ORBITAL NOTATION Try the following:

Oxygen

Magnesium

Sulfur

ELECTRON CONFIGURATIONS

Hydrogen Helium Oxygen Arsenic

ELECTRON CONFIGURATIONS

Beryllium Chlorine Krypton

NOBLE GASELECTRON CONFIGURATION

Phosphorus Cobalt Argon Barium

NOBLE GASELECTRON CONFIGURATION

Silicon Calcium iodine

VALENCE ELECTRONS Valence electrons: The

electrons in an atom’s outermost energy level (orbitals)determine the chemical properties of an element.

ELECTRON DOT STRUCTURES