Electrons and Orbitals

Quantum Mechanics

Describes the arrangement of electrons in atoms in terms of:Main or principal energy levels (n)Orbitals (space occupied within the

atom)How many electrons in each orbital.Basically, gives an address for every

electron in an atom.

Principal Energy Levels (n)

Contain electrons that areClose in energySimilar distance from nucleusHave values of n = 1, 2, 3, 4, 5, 6…..

Orbitals

Orbitals exist within an energy level

All electrons in an orbital have the

same energy

Designated s, p, d, f ..

energy: s<p<d<f

Electron Locations

Main Energy Orbitals inLevels the energy level

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

n=3 3s, 3p, 3d

n=2 2s, 2p

n=1 1s

S P

D

F

Electrons Allowed

All electrons in the same orbital have the same energy.

Within orbitals are sub-orbitals (part of an orbital….like apartments in a building). Each sub-orbital holds 2 electrons.

s orbital 1 sub-orbital = 2 electrons max.

p orbital 3 sub-orbitals = 6 electrons max.

d orbital 5 sub orbitals = 10 electrons max.

f orbital 7 sub-orbitals = 14 electrons max.

S P

D

F

Timberlake LecturePLUS 2000

Electron Configuration

List of subshells containing electronsWritten in order of increasing energySuperscripts give the number of electrons

Example: Electron configuration of neon

number of electrons

1s2 2s2 2p6

Energy level orbital

S P

D

F

Writing Electron Configurations

H

He

Li

C

S

Writing Electron Configurations

H 1s1

He 1s2

Li 1s2 2s1

C 1s2 2s2 2p2

S 1s2 2s2 2p6 3s2 3p4

Learning Check S2

Which if the following is the correct electron configuration for Chlorine?

A. 1s22s22p63s1

B. 1s22s22p63s23p6

C. 1s22s22p63s23p5

D. 1s22p83s1

E. 1s22s22p63s23p7

Solution E2

C. 1s22s22p63s23p5

Timberlake LecturePLUS 2000

Learning Check S3

Using the periodic table, write the complete electronic configuration for each:

A. Be

B. F

C. Mg

Timberlake LecturePLUS 2000

Solution S3

Using the periodic table, write the complete electronic configuration for each:

A. Be

1s2 2s2

B. F

1s2 2s2 2p5

C. Mg

1s2 2s2 2p6 3s2

Orbital

A 3 dimensional space around a nucleus in

which electrons are most likely to be found

Shape represents electron density (not a

path the electron follows)

Each sub-orbital can hold up to 2

electrons.

s orbitals

1s 2s 3s

Three p Sub-Orbitals

px pz py

p orbitals

d sub-orbitals

Review Questions

A. Maximum number of electrons in p orbitalsa) 2 b) 3 c) 6

B. Number of suborbitals in a p orbital.a) 1 b) 2 c) 3

C. Maximum number of electrons in an S orbitala) 1 b) 2 c) 6

Solution

A. Maximum number of electrons in p orbitalsc) 6

B. Number of suborbitals in a p orbital.c) 3

C. Maximum number of electrons in an S orbitalb) 2

Review Questions

• 1) What scientist discovered the nucleus of the atom?

• 2) Who said that electrons travel in ORBITS around the nucleus, like planets around the sun?

• 3) Where in an atom will you find neutrons? Who discovered them?

Review Questions

• 1) What scientist discovered the nucleus of the atom? Rutherford

• 2) Who said that electrons travel in ORBITS around the nucleus, like planets around the sun? Bohr

• 3) Where in an atom will you find neutrons? Who discovered them?

• In the nucleus, tightly packed with the protons; Chadwick