Download The Quantum Mechanical Picture of the Atom

The Quantum Mechanical
Picture of the Atom
ƒ The allowed energy states of atoms
and molecules can be described by sets
of numbers called quantum numbers
n
l
ml
ms
1
Quantum Numbers
„
„
„
n - the principal quantum number
„ n = 1, 2, 3, 4, ......
“shells”
l - the angular momentum quantum number
„
l = 0, 1, 2, 3, … , n – 1 “subshells”
l = s, p, d, f, ......
ml - the magnetic quantum number
„
„
ml = –l, –l + 1, … , l – 1, l
ms - the spin quantum number
„
ms = –½, +½
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Quantum Numbers and Orbitals
„
n +l
„
„
l
„
„
„
Define the energy of the electron
Defines the shape of the orbital
Orbital
„ The volume around the nucleus where
the electron appears 90-95% of the time
The Pauli principle
„ No two electrons in an atom may have
identical sets of four quantum numbers
3
s orbital (l = 0)
„
There is only one s orbital per n level
4
p orbital (l = 1)
„
There are 3 p orbitals per n level
„
They are named px , py , and pz
5
d orbital (l = 2)
„
There are 5 d orbitals per n level
6
f orbital (l = 3)
„
There are 7 f orbitals
per n level
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Order of Orbital Energy
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Building Atoms
1) Build the nucleus by adding the required
# of protons and neutrons according to
the atomic # and mass # of the atom
2) Fill energy levels (orbitals) with the
required # of electrons starting from
the lowest available energy level and
following Pauli and Hund rules (this is
called Aufbau principle)
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Building Atoms - Period 1
n
l
ml
ms
H
He
10
Building Atoms - Period 2
n
l
ml
ms
Li
Be
11
Building Atoms - Period 2
n
l
ml
ms
B
C
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Hund’s Rule
Electrons occupy all the orbitals of a given
subshell (with the same l) singly before
pairing begins. These unpaired electrons
have parallel spins (the same sign of ms).
n
l
ml
ms
C
13
Building Atoms - Period 2
N
O
F
Ne
14
Building Atoms - Period 3
Na
P
Mg
S
Al
Cl
Si
Ar
15
Building Atoms - Period 4
K
Ca
Sc – 4p or 3d ?
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