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 gain energy as they return to lower energy levels emit energy as they return to lower energy levels gain energy as they move to higher energy levels 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?