Evidence of Energy Levels

e-e- Ground state

Excited state

Electrons can only be atspecific energy levels,NOT between levels.

Energy Level

Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 329

AA

BB

CC

DD

Ground state

En

erg

y

Fourexcitedstates

Color = Energy of Photons

Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 329

Spectroscopy

• The science of analyzing matter using electromagnetic emission or absorption spectra.

• Used in many fields of science such as astronomy or forensics.

Atomic Emission Spectrum• A characteristic set of colored lines that is

unique for each element (“fingerprint”)– Different # of electrons

• Caused by the electrons releasing energy as they go from the excited state back down to the ground state– Each line corresponds to a specific photon of

light being emitted

Excited vs. Ground State• Ground State: the lowest possible energy

of an atom described by quantum mechanics

• Excited State: electrons jump to higher energy levels due to an input of energy– It takes a quantum of energy to jump electron

to the next higher energy level– Quantum = amt. of energy needed to move an

e- from one energy level to the next

#7

• When energy is added to an atom, it causes the electrons to jump up to higher energy levels (become “excited”). They release energy when they return to the ground state.

An Excited Lithium Atom

Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 326

Photon ofred lightemitted

Li atom inlower energy state

Excited Li atom

Ene

rgy

Excitation of Hydrogen Atoms

Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 328

Return to Ground State

Frequency A

Frequency B

Frequency C

n = 2

n = 1

n = 3

A

B

C

A + B = C