Topic: Atomic Concepts Aim: and excited state electron configurations?

Topic: Atomic Concepts
Aim: What is the difference between ground state
and excited state electron configurations?
How can we identify unknown elements?
HW:
Ground State vs. Excited State
• States in which e- can exist
• Ground State: lowest energy e- config.
– Shown on Periodic Table
– Innermost PEL fills first, then work outward
Ground State vs. Excited State
• Excited State: e- can move
to a higher PEL 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
Diagram
Elements give off different colors depending on
the amount of energy released
(how far the e- falls)
Neon – Ground vs. Excited State
Examples
• Fluorine
• Ground state e- config (Periodic Table)
– 2-7
• 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 PEL
• 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
Bright Line Spectrum
• Formed from e- falling from excited state
to ground state
• Each element has its own bright-line
spectrum
• Therefore, this is 1 way to ID specific
elements
Ex. The bright-line spectrum of
lithium looks like this:
So, if you have unknown samples & you want to know if 1
of them is lithium, compare the unknown elements’
spectra with the known spectrum for lithium.
More Bright-Line Spectra
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
Flame Test Colors
Sample Questions
1/03 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?