SPECTROSCOPYIdentifying Elements by

Color

Periodic Table: To Date

Atomic Number – and Atomic Mass• Increase left to right

Periodic Table: To Date

Electrons in Valence Shell• Define Chemical Properties

1 e-

8 e-

4 e-2

e-3 e-

Etc.

Periodic Table: Today

Electrons in valence orbits• Define Chemical Properties

Orbit 1Orbit 2Orbit 3Orbit 4Orbit 5

Electrons Electrons around an atom can be found in

different orbits

Each orbit has its own energy level (compared to the nucleus) Low Energy: Close to the nucleus High Energy: Far from nucleus

Electrons When energized, electrons from one energy

level to a higher one around the nucleus of the atom.

They emit energy in the form of electromagnetic radiation (LIGHT!)

If there are an infinite number of electron jumps, a continuous atomic spectrum is created.

Spectral Lines: Colors Light energy travels in waves The wavelength of light determines the color

Emitted Light: More…

Short Waves: HIGH Energy – FAR from nucleus

Long Waves:LOW Energy – CLOSE to nucleus

Spectral Lines: Breaking up Light

Prism – Breaks up white light into a rainbow of colors (a spectrum)

Diffraction Grating – Glass or plastic, ruled with many finely spaced lines (like CD).

Spectral Lines: Emissions from Elements

When energy hits an atom, the energy is absorbed by the electrons and they become “excited” (jump to a higher orbit).

When the electrons jump from the higher orbits back to lower orbits, the energy is emitted as light.

Element Identification: Emitted Light

These spectral lines (lines in a spectrum) are unique to each element, so can be used to

identify them.

Element Identification: Emitted Light

Notice anything about the # of lines in each line spectrum?

TOTAL # electrons ?

H = 1

Li = 3

He = 2

O = 8

C = 6

N = 7

Element Identification: Emitted Light

Why do they have MORE lines than electrons?

H = 1

Li = 3

He = 2

O = 8

C = 6

N = 7

Element Identification: Emitted Light

Why are some lines brighter than others?

H = 1

Li = 3

He = 2

O = 8

C = 6

N = 7

LET’S EXPLORE!!

a) How does the light that astronomers see from distant stars and galaxies tell them that the same atoms with the same properties exist throughout the universe?

b) Which element is not in the star that produced the “unknown spectrum”? How can you tell?

Atomic Emission Spectrum for Unknown Star

Emitted Light: More…

When “energized”, electrons can jump up to higher energy level shells

When they move back down they give off some energy as light

Emitted Light: Colors!

Different wavelengths make different colors !

Let’s EXPLORE!!