Electron Configuration and Emission Spectrum 2017.notebook December 04, 2017

Do Now 1. By looking at the electron configuration, how many principle energy levels does phosphorus Bohr, Electron Configurations and the Bright Line Spectrum have?

Aim: What does the electron configuration tell us about an atom? How and why do atoms become excited and produce 2. How many electrons are in each principle the bright line spectrum? energy level? (I.e.: For oxygen; e‐ configuration (2‐6), it has 2 in the first energy level and 6 in the second energy level.

The electron configuration tells us two things about the atom: 1. How many occupied principle energy levels the element has. 2. How many electrons are in each principle energy level (PEL).

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Bohr's Theory Ground vs. Excited • The electron configuration in the periodic table is called the GROUND 1) Principle energy levels (shells) hold the electrons. STATE configuration. 2) ‐Electrons closer to the nucleus have lower energy (more stable). ‐Electrons farther from the nucleus have higher energy (less stable).

3) Each energy level can only hold a maximum number of electrons based on the following formula: # e= 2n2 ; n= the # of principle energy level

4) A ground state atom has its electrons in the lowest energy levels possible (as close to the nucleus as possible).

Oct 24­6:51 PM Nov 28­4:16 PM 1 Electron Configuration and Emission Spectrum 2017.notebook December 04, 2017

Ground vs. Excited How does an atom produce its characteristic • When electrons absorb energy and move up to higher energy levels, Bright Line Spectrum? this is called an EXCITED STATE.

• It will be different from the ground state in the periodic table. Ground Excited

2­4 2­3­1

• When an electron gains energy it becomes excited and it moves to a higher energy level.

• When the electrons go back d own to their original energy levels they release the absorbed energy as visible light.

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How does an atom become excited? Bright Line Spectrums

Hydrogen • The light produced from a source is put through a prism, the unique color spectrum from each star can be used to determine the composition of the gases on a star

Bright Line Emission Spectrum: Light is emitted (given off) when an excited electron releases energy and returns to it's original ground state. https://www.youtube.com/watch?v=q1O57ZijwPQ

The electron will move from a higher PEL to a lower PEL as it returns to ground state.

Nov 28­4:16 PM Nov 28­4:16 PM 2 Electron Configuration and Emission Spectrum 2017.notebook December 04, 2017

Bright Line Spectrum How are lithium and sodium different in terms of their electrons and electron configurations? • Every element has their own unique spectrum because they have their own unique electron configuration. The have a different number of e‐. The e‐ are arranged differently in the PEL. Hydrogen All elements have a unique electron configuration.

Therefore all elements have an unique bright line spectrum Helium and the bright line spectrum can identify an element. Hydrogen

Carbon Helium

Carbon

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1. Given the following electron configurations, identify each element 3. Write the electron configuration for each of the following elements.

a. 2­8­8­1 ______a. Boron ______b. 2­8­18­5 ______b. Chlorine ______c. 2­1 ______c. Potassium______d. 2­8­18­1 ______d. Zinc______e. 2­8­2 ______e. Iron______

2. Given the following electron configurations, determine whether the atom is in 4. Write the electron configuration for each of the following ions: the ground state or excited state. Also identify each element. a. Li+1 ______c. Ca+2 ______

Ground or excited Name of Element ­2 +3 a. 2­8­16­2 ______b. O ______d. As ______b. 2­4­1 ______c. 2­8­7­1 ______5. Identify the noble gas that each of the above ions are isoelectronic with d. 2­8­1 ______(has a matching electron configuration) e. 2­7­6 ______a. Li+1 ______c. Ca+2 ______

b. O­2 ______d. As3­ ______

Nov 28­4:55 PM Nov 28­4:55 PM 3 Electron Configuration and Emission Spectrum 2017.notebook December 04, 2017

DO NOW

1. Identify the two gases in the unknown mixture.

2. Explain in terms of electrons and energy levels how a bright line spectrum is produced.

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Electron­Cloud Dalton Bohr Thompson Rutherford

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