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Electron Arrangement

Another link for reviewhttp://www.mrcoulter.com/LECTURES/28Elec-config.pdf

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Quantum Numbers

• Quantum numbers specify the properties of atomic orbitals and the properties of electrons in orbitals. This is also known as probable location of electrons about the nucleus of an atom.

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Principal Quantum Number, n

Indicates the main energy level occupied by an electron(n=1,2,3,…7)

http://library.thinkquest.org/C006669/

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Angular momentum quantum number has 4 basic shapes

• The values and shapes are • l = 0 s shape• l = 1 p• l = 2 d• l = 3 f

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Angular Momentum Quantum Number, l

• s shape

sparknotes.com

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p shape

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d shaped orbitals

Courtesy of bluelight.ru

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f orbitals

f orbitals are very complex and you will not be responsible for drawing them. The site below has more informtion.

http://www.d.umn.edu/~pkiprof/ChemWebV2/AOs/ao4.html

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Spin quantum number, s, has only two possible values

• Has only two possible values: +1/2, -1/2.

• See table 2 on page 110 to get a better idea of the number of orbitals and electrons per energy level.

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Electron Configurations

I. Rules Governing Electron ConfigurationsII. Orbital NotationIII. Electron-Configuration Nottion

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Rules Governing Electron Configurations

I. Aufbrau Principle – an electron occupies the lowest-energy orbital that can receive it.

Source: https://chemistry.twu.edu/tutorial/AufbauSum.html

This is really a thought process in which we think about building up an atom from the one that preceeds it in atomic number, by adding a proton and neutrons to the nucleus and one electron to the appropriate atomic orbital.

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II. Pauli Exclusion Principle – no two electrons in the same atom can have the same set of four quantum numbers.

Rules Governing Electron Configurations, cont.

The box at left shows the different spin states of two electrons in the same orbital. This drawing is the electron configuration of a helium atom’s 1 s orbital.

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Rules Governing Electron Configurations, cont.

III. Hund’s Rule – orbitals of equal energy are each occupied by one electron before any orbital is occupied by a second electron, and all electrons in singly occupied orbitals must have the same spin state.

en.citizendium.org

14Source: chem.wisc.edu

Periodic Table: Orbitals

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Orbital Notation

Source: naturalphilosophers.org

Pair of electrons in an orbital

Unpaired electron

Orbital name

What element is this showing?Fluorine

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Sample problems

Write the electron configuration notation for Silicon and Scandium (use the Aufbrau diagram)Si has 14 electrons2 in 1s 2 in 2s6 in 2p 2 in 3s 2 in 3p written as:1s2 2s2 2p6 3s2 3p2

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Scandium Electron Configuration Notation

Sc has 21 electrons

1s2 2s2 2p6 3s2 3p6 4s2 3d1

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Scandium Notations

Electron Configuration Notation1s2 2s2 2p6 3s2 3p6 4s2 3d1

Orbital Notation__ __ __ __ __ __ __ __ __ __ __ __ __ __ ___

1s 2s 2p 3s 3p 4s 3d

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Notations,cont.Noble gas notation – back up to the last noble gas prior to the element

and add orbitals:[Ar}4s23d1

Dot notation - shows only the outer shell electrons for an element’s atom (maximum number of e’s in an outer shell is 8) for Sc: 4s2 for F: 2s22p5 for Ne: 2s22p6

.. . . Sc : : F : : Ne : . . .

Other info: atoms are more stable when they have a half-filled or completely

filled outer shell

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Remaining Ch5 asgns. From book

• 137/1-3; 149/1-5; 165/1-3• 166/1-15 (use periodic chart)• 166/17a-c,18a-c,19c-e,20,21a-c• 167/24-29,32,34• 167/35-40