Electrons try to be as close to nucleus as possible = All three - - PDF document

1

Three ways to write electron configuration

• 1. full electron notation
• 2. Noble gas core notation

K = Cl = 1s2 Cl = 1s2 2s2 Cl = 1s2 2s2 2p6 Cl = 1s2 2s2 2p6 3s2 Cl = 1s2 2s2 2p6 3s2 3p5 K = 1s2 K = 1s2 2s2 K = 1s2 2s2 2p6 K = 1s2 2s2 2p6 3s2 K = 1s2 2s2 2p6 3s2 3p6 K = 1s2 2s2 2p6 3s2 3p6 4s1 Cl = K = Cl = [Ne] Cl = [Ne] 3s2 Cl = [Ne] 3s2 3p5 K = [Ar] K = [Ar] 4s1

Valence electrons = outer shell e-, determine C and P prop.

• f elements
• Orbitals indicated by boxes/lines
• Each e- indicated by arrow: ↑ or ↓
• An orbital can hold up to 2 e- but they must

have opposite spins

= Pauli Exclusion Principle

• 3. Orbital or Box Diagram

Electrons can spin in two directions:

↑ ↓

Hund’s Rule = e- fill orbitals singly with

parallel spins until 1/2-filled, then pair up with opposite spins

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

__ __ __ __ __ __ __ __ __ Cl = K = __ __ __ __ __ __ __ __ __ __

1s 2s 2p 3s 3p All three 3p orbitals have similar E level 3px 3py 3pz 2px 2py 2pz

degenerate orbitals =

Orbitals with similar E levels Ex-

• all ____ orbitals (2px, 2py, 2pz) in 2p sublevel are

degenerate

3 5

• all ____ orbitals in a ‘d’ sublevel are degenerate

P = __ __ __ __ __ __ __ __ __

• Electrons try to be as close to nucleus as possible =

lowest PE

• Electrons fill lowest E orbitals first then fill higher E
• rbitals
• Lowest E orbitals are closest to nucleus and smallest
• Highest E orbitals are furthest from nucleus and largest

For a given shell (E level), filling order is: s → p → d → f

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1s→ 2s→ 2p→3s→3p→4s→3d→4p→5s→4d→5p→ 6s→4f→ 5d→6p→ 7s→ 5f→ 6d→ 7p

Subshell Filling Order

Lowest E Highest E

d sublevel lags one period behind f sublevel lags two periods behind Fe:

1s2 1s2 2s2 1s2 2s2 2p6 1s2 2s2 2p6 3s2 1s2 2s2 2p6 3s2 3p6 1s2 2s2 2p6 3s2 3p6 4s2 1s2 2s2 2p6 3s2 3p6 4s2 3d6

Shape of Orbitals

• s orbitals are spherical
• p orbitals are figure eight shaped (2 lobes)
• d orbitals are cloverleafed (4 lobes)

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An atom has: 2 e- in 1st energy level 8 e- in 2nd energy level 7 e- in 3rd energy level Which element is it?

1s 2s 2p 3s 3p

? = Cl

Total # e- in p-orbitals? How many unpaired e- are there? Total number of e- in s-orbitals? 11 1 6

__ __ __ __ __ __ __ __ __ __

Ions

F = 1s2 2s2 2p5 Na = 1s2 2s2 2p6 3s1 F- F- = 1s2 2s2 2p6 Na+ = 1s2 2s2 2p6 # valence electrons 7 8

F- has same configuration as a noble gas

Na+ has same configuration as 1 8 Electron configuration

(Ne) (Ne)

Na Na+ Na+, F- and Ne all have the same configuration isoelectric = atoms/ions with same e- configuration These ions are all isoelectric: [Ne] 3s23p6 Ca+2 Ar Cl-1 S-2 K+1 Ca: [Ar] 4s2 K: [Ar] 4s1 Ar: [Ne] 3s23p6 Cl: [Ne] 3s23p5 S: [Ne] 3s23p4 Atoms:

Excited state electron configuration

• When an e- is in a higher E level than normal
• Happens when element heated or exposed to

electrical current

• e- jump from inner shell orbital (low E) to
• uter shell orbital (higher E)
• What happens when e- falls back to appropriate
• rbital?

Gives off EM radiation (light) F = [He] 2s2 2p4 3s1 Excited state F = [He] 2s2 2p5 Ground state

light

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1s2 2s2 2p6 3s1 1s2 2s2 2p6 3s2 3p4 3s1 1s2 2s1 2p6 1s2 2s2 2p6 3s2 3p6 4s1 1s2 2s1 2p6 3s2 3p2 Excited or ground state? ground excited excited ground excited 1s2 2s2 2p6 3s2 3p4 3s1 1s2 2s1 2p6 1s2 2s1 2p6 3s2 3p2 1s2 2s2 2p6 3s2 3p5 1s2 2s2 2p5 1s2 2s2 2p6 3s2 3p1

1

1 s 2

2

2s 2p 2 6

3

3s 3p 3d 2 6 10

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4s 4p 4d 4f 2 6 10 14 Energy Level Allowed subshells #electrons insubshell # orbitals in subshell 1 1 3 1 3 5 1 3 5 7

Summary of electron configuration