Download Quantum Model and the Aufbau rule

Modern Theory of the Atom:
Quantum Mechanical Model
Recap of Bohr Model
electrons:
particles moving in circular orbits with specific speed, position, & energy
energy levels possess specific quantum of energy
electrons can move between energy levels
higher energy levels farther from nucleus
• e- moving up to higher E level: electron absorbs energy
• e- moving down to lower E level: electron emits light energy
ground state:
electrons located in lowest possible energy levels, closest can be to
nucleus
Bohr Model vs. Modern Theory
• electron = particle
• e- path is orbit
– holds 2n2 electrons
• electron = wave
• e– path is orbital
– holds 2 electrons
• circular path
• not necessarily circular
• each energy level
• each energy level has
has specific energy
specific energy
• can find exact
• probable location of eposition/ speed of e-
Orbital – Modern Theory
• orbital: term describes region where e- might
be found
• each orbital:
– specific energy & specific shape
– described by 4 parameters of wave function
(like an address)
• quantum numbers = n, l, m, s
• structure of orbitals explain:
– bonding, magnetism, atom size, crystal structure
n: principal quantum number
• specifies atom’s principal energy levels
• whole number values: 1, 2, 3, 4, …
• 2n2 = maximum # e- in any principal
energy level
l=
describes sublevels
• sublevels are labelled by shape:
–s, p, d, f
s orbitals:
spherical
p orbitals: dumbbell shaped
d orbitals: complex shapes
f orbitals: complex shapes too
Sublevels
1st principal energy level:
s (1 sublevel)
2nd level:
s,p (2 sublevels)
3rd level:
s,p,d (3 sublevels)
4th level:
s,p,d,f (4 sublevels)
m = 3rd quantum number (orbitals)
• each sublevel contains 1 or more orbitals
• each orbital holds a max of 2 electrons
•
•
•
•
s has 1 orbital
p has 3 orbitals
d has 5 orbitals
f has 7 orbitals
2 electrons)
1st PEL =s (1 sublevel) = 1 orbital (__
2nd PEL =s,p (2 sublevels) = 4 orbitals (__8 e-)
3rd PEL = s,p,d (3 sublevels) = 9 orbitals (___
18 e-)
32 e-)
4th PEL s,p,d,f (4 sublevels) = 16 orbitals (___
4th quantum number = s
• e- spin: 2 possible values
– clockwise and counter clockwise
– Illustrated by arrows with opposite directions

address for each electron
• 4 quantum numbers
• no 2 e- can
– occupy same space in atom
– have same 4 quantum numbers
max 2 electrons per orbital
(Pauli exclusion principle)
Memorize
s
1
2e-
s
p
d
f
p
3
6e-
d
5
10e-
f
7
14e-
sublevels
# of orbitals
max # of electrons
*each orbital holds 2 e-
electron configurations
• add e- to atoms starting with
lowest energy levels (most stable)
– start with 1s, then work
upward increasing in energy
• follow Aufbau Principle.
3rd principal energy
level, 3 sublevels
2nd principal energy level, 2 sublevels –
s&p

1st principal energy level, 1 sublevel – s
Each box represents an orbital and holds 2 electrons
Aufbau Principle
1s
2s
3s
4s
5s
6s
7s
follow arrows
2p
3p
4p
5p
6p
7p
3d
4d
5d
6d
7d
4f
5f
6f
7f
sequence of orbitals:
1s, 2s, 2p, 3s, 3p, 4s,
3d, 4p, 5s, 4d, …
exceptions do occur:
- half-filled orbitals
have extra stability
- magic # is 8
2
1s2
1s
He
2s2 2p6
3s2 3p6 3d10
2 2s2 2p2
1s
C
4s2 4p6 4d10 4f14
5s2 5p6 5d10 5f14
2 2s2 2p6 3s2
Mg
1s
6s2 6p6 6d10
7s2 7p6 7d10
Zn
1s2 2s2 2p6 3s2 3p6 4s2 3d10
from modern configurations can figure out Bohr configurations: add e- in each energy level (shell)
He 1s
2
1=2
2
C
1s22s22p2
1=2
2 = 2+2
2–4
Mg
Zn
1s22s22p63s2
1=2
2 = 2+6
3=2
2–8–2
1s22s22p63s23p64s23d10
1 = 2 2 = 2+6 3 = 2+6+10
2 – 8 – 18 – 2
4=2
Hund’s Rule
• most e- with same spin, so if more than one
same orbital:
e- fill orbitals one at time before pairing up
ex: oxygen
• 1s2
2s2
2p4
Which element? boron
How many unpaired e-? 1
How many principal energy level’s occupied?
How many principal energy level’s are fully
occupied? 1
How many sublevels contain e-? 3
How many sublevels full? 2
How many orbitals contain e-?
3
2