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