Ch7 Lec6

(4/28/20, bes)

Greetings,

I wanted to post this last lecture well before exam 3 (Friday, May 1st) so that you do not feel too rushed...review these notes as time permits. This is the last lecture for Chapter 7. There is an additional WA up as well...this WA has some error in counting point...i will fix this later.

Multi-electron Energy Levels

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The figure above was presented in yesterday's notes...building upon this...please notice:

The shift in the energy levels mixes up the order in which the orbitals are filled.

- the 3d orbitals are now above the 4s orbitals

- the 4d orbitals are now above the 5s orbitals (not shown in figure)

- the 5d orbitals are now above the 6s orbitals (not shown in figure)

Filling electrons into orbitals

For boron (B) (as previously discussed), it contains 5 electrons...with 2 electrons per orbital, then the electron configuration is: 1s² 2s² 2p¹.

(Note: in WA i would ask that you enter the answer as, 1s2 2s2 2p1 <-- no superscripts).

For carbon (C) (as previously discussed), it contains 6 electrons...with 2 electrons per orbital, then the electron configuration is: 1s² 2s² 2p².

(Note: in WA i would ask that you enter the answer as, 1s2 2s2 2p2 <-- no superscripts).

For neon (Ne), it contains 10 electrons...with 2 electrons per orbital, then the electron configuration is: 1s² 2s² 2p⁶.

(Note: in WA i would ask that you enter the answer as, 1s2 2s2 2p6 <-- no superscripts).

For argon (Ar), it contains 18 electrons...with 2 electrons per orbital, then the electron configuration is: 1s² 2s² 2p⁶ 3s² 3p⁶.

(Note: in WA i would ask that you enter the answer as, 1s2 2s2 2p6 3s2 3p6 <-- no superscripts).

**things get a bit different at this point...as stated the 3d orbitals shifted up in energy, so we fill the 4s orbitals before we fill the 3d orbitals

For calcium (Ca), it contains 20 electrons...with 2 electrons per orbital, then the electron configuration is: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s².

(Note: in WA i would ask that you enter the answer as, 1s2 2s2 2p6 3s2 3p6 4s2).

For scandium (Sc) - the first "transition metal", it contains 21 electrons...with 2 electrons per orbital, then the electron configuration is: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹.

(Note: in WA i would ask that you enter the answer as, 1s2 2s2 2p6 3s2 3p6 4s2 3d1).

The Build-Up Principle

Electron configuration can be summaries in the following version of the periodic table:

1s --> 2s --> 2p --> 3s --> 3p --> 4s --> 3d --> 4p --> 5s --> 4d --> 5p --> 6s --> 4f --> 5d --> 6p --> 7s --> 5f --> 6d --> 7p

Often times the f-orbitals are left out of the periodic table, since it just makes it too long...and does not print out well on the inside cover of your textbook!

1s --> 2s --> 2p --> 3s --> 3p --> 4s --> 3d --> 4p --> 5s --> 4d --> 5p

The 'periodic table can be in the 32-column format:

or as in the standard format:

Practice Problems

Q: What is the electron configuration for oxygen (O)?

A: 1s² 2s² 2p⁴ or in WA --> 1s2 2s2 2p4

Q: What is the electron configuration for chlorine (Cl)?

A: 1s² 2s² 2p⁶ 3s² 3p⁵ or in WA -->1s2 2s2 2p6 3s2 3p5

Q: What is the electron configuration for argon (Ar)?

A: 1s² 2s² 2p⁶ 3s² 3p⁶ or in WA -->1s2 2s2 2p6 3s2 3p6

'As you might notice, these electron configurations can get a bit long...so there is a shorthand notation that uses the noble gases as a starting point...

The electron configuration for argon (Ar) can be written as [Ar], therefore, the electron configuration for potassium (K) can be written as [Ar] 4s¹ or in WA --> [Ar] 4s1.

Q: What is the electron configuration for bromine (Br)?

A: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁵ or in WA -->1s2 2s2 2p6 3s2 3p5 4s2 3d10 4p5

A (shorthand notation): [Ar] 4s² 3d¹⁰ 4p⁵ or in WA --> [Ar] 4s2 3d10 4p5

Q: What is the electron configuration for strontium (Sr)?

A: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² or in WA -->1s2 2s2 2p6 3s2 3p5 4s2 3d10 4p6 5s2

A (shorthand notation): [Kr] 5s² or in WA --> [Kr] 5s2

Q: What is the electron configuration for gold (Au) - it has f-electrons....?

You may use shorthand notation unless stated.

END of Chapter 7...end of exam 3 material.