Topic #9 : Ground State vs. Excited State

What is the difference between ground state and excited state electron configurations?

How can we identify unknown elements?

Ground State vs. Excited State

• States in which e- can exist

• Ground State: lowest energy e- config.– Shown on Periodic Table– Innermost energy level fills first, then work

outward

Ground State vs. Excited State

• Excited State: e- can move to a higher energy level without filling the lower energy level first– Do this by absorbing energy

• Excited e- fall back to ground state by releasing energy

• Energy released called quanta or quantum• Quanta/Quantum small, specific

amounts of energy.

Diagram

Elements give off different colors depending on the amount of energy released

(how far the e- falls)

Neon – Ground vs. Excited State

Working with your face partner, write down another excited state electron configuration for neon. (write it in your notes)

Examples

• Fluorine. How many protons? Electrons?• Ground state e- config (Periodic Table)

– 2-7• Working with your shoulder partner write 2

possible excited state e- configs– 1-7-1– 2-6-1– 1-8

• Note how an inner level is left partially filled b/c an e- has jumped to a higher energy level

• Note that TOTAL # OF e- REMAINS THE SAME!

Sample Questions

1. Which is the electron configuration of an atom in the excited state?

A) 2 – 8 – 2 C) 2 – 7 - 1

B) 2 – 8 – 1 D) 2 – 8 – 3

2. Which electron configuration represents an atom in the excited state?

A) 1 – 2 C) 2 - 3

B) 2 – 1 D) 2 - 7

Also works with e- conf.

• Oxygen 1s22s22p4 ground state

»1s12s22p5 possible excited state

»1s22s12p5 possible excited state

»2,6 ground state

»1, 7 excited state

Flame Test

• Another way to ID elements

• Element heated

• e- move to excited state (due to absorbing energy)

• e- fall back to ground state (due to releasing energy)

• Flame turns color specific to that element

So How Much Energy ???E = h

is the frequency

h is Planck’s constant (6.626 x 10 -34 J)

Sometimes you are given wavelength not frequency; however, you can still solve for it. Frequency and wavelength are related by the following equation:

C = λ

Where c is the speed of light (3.00 x 10 8 m/s )

λ is the wavelength

is the frequency As Energy increases so does the frequency, but as the frequency increases the wavelength decreases

A photon is emitted from an atom with an energy of 4.05 x 10-19 J. What is the wavelength of the photon using correct significant figures?

(speed of light = 3.00 x 10 8 m/s and Planck’s constant = 6.626 x 10 -34 J•s )

E = h C = λ (formulas)

Given: E= 4.05 x 10-19 J

c= 3.00 x 108 m/s

h= 6.626 x 10-34 J•s

Unknown: λ (wavelength)

Equation: E = h C = λSubstitute: λ = c /, but we do not know however we can calculate it with the

other formula. E / h.

4.05 x10-19 J /6.626 x 10-34 J•s now that you know you can substitute into other equation

6.11 x 1014 1/s λ = 3.00 x 108 m/s / 6.11 x 1014 1/s

Solve: λ = 4.90814 x 10-7 m or 4.91 x 10-7 m

Flame Test Colors

Sample Questions1/03 During a flame test, ions of a specific metal are heated

in the flame of a gas burner. A characteristic color of light is emitted by these ions in the flame when the electrons

(1) gain energy as they return to lower energy levels(2) emit energy as they return to lower energy levels (3) gain energy as they move to higher energy levels(4) emit energy as they move to higher energy levels

Which electron configuration represents the excited state of a calcium atom?

What is the element Z?