Electron Configurations

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Transcript Electron Configurations

Electron Configurations Of Atoms & Ions

Men & their Rules

• Aufbau Principle: Start at the beginning (Electrons enter lowest energy level 1 st ) • Pauli Exclusion Principle: Only 2 allowed (Only 2 electrons allowed in any orbital) • Hund’s Rule: Stay solo as long as possible (For orbitals of equal energy, 1 electron enters each until all orbitals contain one before any pairs up.)

Consequences of Aufbau Principle

• Electrons enter orbitals in order of increasing energy levels.

• This order is shown in text on page 111.

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

But there are two exceptions, namely Cu & Cr, who subtract 1 from 4s and add it to 3d.

Consequences of Pauli exclusion

• The

s

orbital is filled with 2 electrons.

• The 3 different orientations of the

p

orbital,

p x

,

p

y , &

p z

, each contain a max of 2 electrons • The 5 different orientations of

d

orbitals,

d

xy

d

xz ,

d

y z ,

d x 2 y 2

, &

d

z 2 , can have max of 2 each.

• The 7 different orientations of

f

orbitals also only have 2 electrons for each suborbital.

Consequences of Hund’s Rule

• One electron is added to

p

x , then 1 to

p

y , then 1 to

p

z , before the second one is added to

p

x . The 5 th electron is then added to

p

y , & 6 th to

p

z .

• The same pattern is observed for the

d

&

f

suborbitals.

• NOTE: The single electrons all have parallel spins. When the 2 nd electron is added to each suborbital, it spins in the opposite direction.

Relating this to the periodic table:

• The “

s

block” = Groups IA & IIA • The “

p

block” = Groups IIIB – VIII (13-18) • The “

d

block” = Transition elements (Groups IIIA-IIB; Groups 3-12) • The “

f

block” = Rare earth metals

What this means…

• You merely need to follow the periodic table to figure out electron configurations.

• The block (

s, p, d,

&

f

) indicates where the last electrons go.

• Follow the period numbers, 1-7, because these are your energy levels & then remember suborbitals penetrate differently.

d

block starts at 3

d

;

f

block starts at 4

f

How can we apply this?

• Follow the periodic table numerically – 1

s

2 (takes you to He) 2

s

2 (to Mg) 3

p

6 (to Ar) 4

s

2 (to Be) 2 (to Ca) 3

d p

1-3 6 (to Ne) 3 (to V) ***

s

2 – Cr (1 st exception): 1

s

2 2

s

2 2

p

6 3

s

2 3

p

6 4

s

1 3

d

5 – Cu (2 nd exception): 1

s

2 2

s

2 2

p

6 3

s

2 3

p

6 4

s

1 3

d

10 • Mn: 1

s

2 2

s

2 2

p

6 3

s

2 3

p

6 4

s

2 3

d

5 • Zn: 1

s

2 2

s

2 2

p

6 3

s

2 3

p

6 4

s

2 3

d

10 – Ga: 1

s

2 2

s

2 2

p

6 3

s

2 3

p

6 4

s

2 3

d

10 4

p

x 1

Applications,

continued

• La is beginning of the lanthanide series – 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 5d 1 • The pattern slightly changes with Ce – 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 5d 1 4

f

1 • Pr puts it back on track – 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 4

f

3 – This is because 4

f

and 5

d

are close in energies

Noble Gas Configurations

• Instead of writing entire core electron configuration of the noble gas, one can abbreviate it [NG] & write only valence e • Al: 1

s

2 2

s

2 2

p

6 3

s

2 3

p x

1 or [Ne]3

s

2 3

p x

1 • Ag:1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 9 or [Kr]5s 2 4d 9 • Am:1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 4

f

14 5

d

10 6

p

6 7

s

2 5

f

7 or [Rn] 7

s

2 5

f

7 • Sg: [Rn]7

s

2 5

f

14 6

d

4 86+2+14+4 =106= Sb atomic#

Orbital Notations

• • • • • This shows all 4 quantum numbers

n

(principle quantum #) = energy lvl 1,2,3...

l m

(angular momentum Q.N.) = shape (magnetic Q.N.) =

x, y, z

for

p s,p,d,f

, etc…

s

(spin Q.N.) = +1/2 (cw) or -1/2 (ccw) shown as upward or downward arrows 16 8 O ___ ___ ___ ___ ___ 1s 2s 2p x y z