In your own words describe why its better to describe the movement of electrons as an

electron cloud rather than orbitals.

How do you excite an electron?

Electromagnetic Spectrum

Background• Neils Bohr

– Danish Physicist– Proposed a “planetary”

model of the atom– Theorized that

travel in orbits around

the nucleus

Electrons in Orbit?

• Bohr suggested that electrons “jump” between energy levels (orbits)

• When an atom absorbs or gives off energy, the electron jumps to a higher or lower orbit.– It absorbs energy as it moves up to a higher orbit

– It gives off energy as it moves down to a lower orbit• This energy is given off as heat or light• This energy given off travels in the form of waves• Also called an emission of an photon

+

Emission of photon

Absorption of energy

E5

E4

E3

E2

E1

+

E – 0.85

E – 01.51

E – 3.40

E – 13.60

E – 0.54

E5E4

E3

E2

E -0.85E -1.51

E -3.40

E1

E -13.60

+

To calculate the amount of energy between energy levels:

Just subtract the initial energy state from the final.

E5 to E1: _-.54______ - _-13.6___ = 13.06

E3 to E1:_-1.51__- _-13.60___= 12.09

E4 to E2:_-.85_-__-3.40__= 2.55

E5 to E2:_-0.54__-_-3.40__= 2.86

E – 0.54

434mn

410mn

656mn

486mn

_________________________________

400 500 600 700

E5E4

E3

E1

E -0.85

E -1.51

E -3.40

E -13.60

+

E – 0.54

434mn

410mn

656mn

486mn

_________________________________

400 500 600 700

E2

The Electromagnetic Spectrum You actually know more about it than you may think!

• The electromagnetic spectrum (EM) is just a name that scientists give all the different types of radiation when they want to talk about them as a group.

• Radiation is energy that travels and spreads out as it goes– visible light that comes from a lamp in your house– radio waves that come from a radio station

• Hotter, more energetic objects and events create higher energy radiation than cool objects.

• Wavelength is

the distance from crest to

crest of a wave

• The frequency of a wave is the number of waves that pass a given point one second

Electron Energy

• The longer the

wavelength the

lower frequency

• The shorter the wavelength the higher the frequency

The Electromagnetic Spectrum• Radio:

– the same kind of energy that radio stations emit into the air

– also emitted by stars and gases in space• Helps astronomers learn what they are made of.

• Microwaves: – They will cook your popcorn in

just a few minutes! – Microwaves in space are used

by astronomers to learn about the structure of nearby galaxies, our own Milky Way!

• Infrared:

– Our skin emits infrared light

– In space, Infrared light maps the dust between stars

The Electromagnetic Spectrum

• Visible Light: – This is the only section of the EM that can be

seen by our eyes. – Visible radiation is emitted by everything from

fireflies to light bulbs to stars ... also by fast-moving particles hitting other particles.

The Electromagnetic Spectrum

• Ultraviolet: – The Sun is a source of ultraviolet

(or UV) radiation– Stars and other "hot" objects in

space emit UV radiation. X-rays:• Your doctor uses them to look at your bones and your dentist to look at your teeth.

• Hot gases in the Universe also emit X-rays .

Gamma Rays: – Radioactive materials (some natural and

others made by man in things like nuclear power plants) can emit gamma-rays.

– Big particle accelerators that scientists use to help them understand what matter is made of can sometimes generate gamma-rays.