Modern Model of the Atom

Quantum Mechanical Model

• Does not describe the movement of the electrons, only where they are at any point in time.

• Orbital – a region in which an electron will have the greatest probability of being found. (Any orbital can hold two electrons.)

Quantum Numbers

• Set of 4 numbers describes everything you need to know to find an electron. (Tells its address.)

Principle quantum number (n)

• Tells the distance from the nucleus• The main energy level• Numbers 1-7• Corresponds to rows on the

periodic table

5

Number of Electrons

• The total number of electrons that CAN be held in a principle energy level is

2n2

• Example: The 5th principle energy level can hold 2(52) = 50 e-

Orbital Quantum Number

• s – 1 in a principle energy level

• p – 3 in a principle energy level

Orbital Shapes Continued

• d – 5 in a principle energy level

• f – 7 in a principle energy level

4 of this type 1 of this type

Finding Orbital Quantum #s on the Periodic Table

S Block

D Block

P Block

F Block

Magnetic Quantum Number

• Tells the position in space.

• s – 1 position (2 e- total)

• p– 3 positions (6 e- total)

• d – 5 positions (10 e- total)

• f – 7 positions (14 e- total)

Spin Quantum Number

• Tells the direction of spin.

• Pauli Exclusion Principle: No two electrons can have the same of Quantum Numbers

ORBITAL NOTATIONS AND ELECTRON CONFIGURATIONS

Filling Order

• The “s” shape starts in principle energy level 1.

• p in 2

• d in 3

• f in 4

Filling Order Continued

• The “d” shapes are 1 row lower than they are supposed to be.

• The “f” shapes are 2 rows lower.

Finding Orbital Quantum #s on the Periodic Table

S Block

D Block

P Block

F Block

Orbital Notation

• Shows all four quantum numbers for every electron in the atom.

• A box or line is one orbital.

• An arrow is one electron.

Orbital Notation for Silicon

• Silicon has 14 electrons, so you will draw 14 arrows.

1s 2s2p

3s3p

More Examples:

1s 2s 2p 3s

Magnesium

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

1s 2s 2p 3s 3p

Copper

Chlorine

18

Electron Configurations

• Shorthand versions of orbital notations.

• Does not indicate the magnetic or spin quantum numbers.

• Tells the total number of electrons in each SET of orbitals.

19

Writing an Electron Configuration

• Write the electron configuration for Neon.

11s222s222p6

Principle Quantum NumberPrinciple Quantum NumberSubshell

Total Number of Electrons

20

Your Turn

• Write the electron configuration for Potassium.

• Write the electron configuration for Copper

• Write the electron configuration for Bromine

21

Answers

• Potassium

1s22s22p63s23p64s1

• Copper

1s22s22p63s23p64s23d9

• Bromine

1s22s22p63s23p64s23d104p5

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Excited State Electrons

• You can also draw and recognize elements with electrons in the excited state from an electron configuration.

• For example: What element is shown? 1s22s22p63s13p1

23

What did you answer?

• This is NOT Aluminum (Al), this is Magnesium (Mg) in the excited state!!

• Why?

• Look at the 3s sublevel… 1s22s22p63s13p1