Subshells and Orbitals

8/11/2019 Subshells and Orbitals

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Timberlake LecturePLUS 2000

Subshells and Orbitals


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Quantum Mechanics

Describes the arrangement of electrons

in atoms in terms of:

Main or principal energy levels (n)

Energy subshells

Orbitals (space occupied within the

atom)


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Principal Energy Levels (n)

Contain electrons that are

Close in energy

Similar distance from nucleusHave values of n = 1, 2, 3, 4, 5, 6..

Maximum number of electrons = 2n2

n =1 2(1)2 = 2

n =2 2(2)2 =8

n=3


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Energy Levels (Shells)

A group of electrons in an atom all having the

same principal quantum number (n)

n = 1, 2, 3,

The first shell (n = 1) is lowest in energy,

2ndlevel next and so on 1


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Energy Levels for Electrons

Some possible electron transitions for the first

three energy levels are shown below. The

negative value means that the electron in the

atom has a lower energy than a free electronEnergy Level Energy, E

n=3 ___________________ (-) 2.420 x 1019J

n=2 __________________ (-) 5.445 x 1019J

n=1 __________________ (-) 2.178 x 1018

J


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Learning Check S1

A. What energy change (J) takes place when an

electron in a hydrogen atom moves from the

first (n=1) to the second shell (n=2)?

B. What energy change (J) takes place when

the electron moves from the third shell to thesecond shell?


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Solution S1

A. What energy change takes place when an

electron in a hydrogen atom moves from the

first (n=1) to the second shell (n=2)?

1.634 x 10-18J of energy must be absorbed.

B. What energy change takes place when the

electron moves from the third shell to the

second shell?(-5.445 x 10-19J)-(2.2420 x 10-19J)= -3.025 x

1019J will be em it ted as electro n fal ls from a

higher to a lower energy state


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Subshells

Energy sublevels within energy level

All electrons in a subshell have the

same energy

Designated s , p , d , f ..Sublevel energy: s


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Electron Locations

Main

Energy

Levels Sublevels

n=4 4s, 4p, 4d, 4f

n=3 3s, 3p, 3d

n=2 2s, 2p

n=1 1s


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Sublevels in n = 1,2, 3

3d

n = 3 3p

3s

2p

n = 2 2s

n = 1 1s


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Electrons Allowed

All electrons in the same sublevel have the sameenergy.

All 2s electrons have the same energy. All 2p

electrons have the same energy which is slightlyhigher than the energy of the 2s electrons

s sublevel 2electrons

p sublevel 6electronsd sublevel 10electrons

f sublevel 14electrons


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Electron Configuration

List of subshells containing electrons

Written in order of increasing energy

Superscripts give the number of electrons

Example: Electron configuration of neon

number of electrons

1s2 2s2 2p6

main shell subshell


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Order of Filling

Total energy of a subshell =energy of the main shell + the subshell

The 4s energy < 3d energy

4p ___

3d ___ (finishes the n=3 shell)

4s ___ (starts the n=4 shell)

3p ___

3s ___

2p ___

2s ___

1s ___


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Writing Electron Configurations

H 1s1

He 1s2

Li 1s2 2s1

C 1s2

2s2

2p2

S 1s2 2s2 2p6 3s2 3p4


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Sublevel Blocks

s1 s2 p1p2 p3 p4p5p6

1

2

3 d1- d10

4

56

f1- f14


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Find the element on the periodic

table

Use the order of filling indicatedacross each period

Groups 1-2 = s level

Groups 3-8 = p levelTransition = d level

Lantanides = f level

Periodic Table and Electron

Configuration


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Learning Check S2

Indicate if each configuration is (1) correct or

(2) incorrect for potassium. Give an

explanation for selection of 1 or 2. Explain

why or why not?

A. 1s22s22p63s1 1 or 2

B. 1s22s22p63s23p6 1 or 2

C. 1s22s22p63s23p64s1 1 or 2

D. 1s22p83s1 1 or 2

E. 1s2

2s2

2p6

3s2

3p7

1 or 2


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Solution E2

For phosphorus,indicate if each

configuration is (1) correct or (2) incorrect.

Explain why or why not.

A. 2, 2, 8, 5 2

B. 2, 8, 3 2

C. 2, 8, 5 1

D. 2, 6, 7 2


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Learning Check S3

Using the periodic table, write the complete

electronic configuration for each:

A. Cl

B. Sr

C. I


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Solution S3

Using the periodic table, write the complete

electronic configuration for each:

A. Cl1s22s2 2p63s23p5

B. Sr

1s22s2 2p63s23p64s23d10 4p65s2

C. I

1s22s2 2p63s23p64s23d10 4p65s2 4d105p5


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Learning Check S4

A. The final two notations for Co are

1) 3p64s2

2) 4s2

4d7

3) 4s23d7

B. The final three notations for Sn are

1) 5s25p24d10

2) 5s24d105p2

3) 5s25d105p2


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Solution S4

A. The final two notations for Co are

3) 4s2 3d7

B. The final three notations for Sn are

2) 5s2 4d10 5p2


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Orbital

A 3 dimensional space around a nucleus in

which electrons are most likely to be found

Shape represents electron density (no t a

path the electron fol low s)

Each orbital can hold up to 2 electrons.


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s orbitals

1s 2s 3s


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Three p Orbitals

px pz py


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p subshell contains p orbitals


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d orbitals


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Learning Check S5

A. Number of electrons in a p orbital

1) 1e 2) 1e or 2e 3) 3e

B. Number of orbitals in a p subshell1) 1 2) 2 3) 3

C. Number of orbitals in 4d subshell

1) 1 2) 3 3) 5

D. Number of electrons (maximum) in a 3dsubshell

1) 2e 2) 5e 3) 10e


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Solution S5

A. Number of electrons in a p orbital

2) 1e or 2e

B. Number of orbitals in a p subshell

3) 3

C. Number of orbitals in 4d subshell3) 5

D. Number of electrons in a 3d subshell

3) 10e

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Subshells and Orbitals

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