Quantum Mechanics - South Kingstown High School

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Transcript Quantum Mechanics - South Kingstown High School

Quantum Mechanics
n = The principle quantum number
Describes the possible energy levels and
pictorially it describes the orbital size.
n = 1, 2, 3…. where an energy level with the value of 2
is larger than one with the value of 1.
1s
2s
l
Quantum Mechanics
= angular momentum quantum number
Describes the "shape" of the orbital and can have values
from 0 to n - 1 for each n.
orbital designation :
s
p
d
f
Too hard to draw
see text
shape :
ml = magnetic quantum number
Related to the orientation of an orbital in space relative to
the other orbitals with the same l quantum numbers. It
can have values between l and - l .
ms = spin quantum number
An electron has either +1/2 or -1/2 spin values; sometimes
referred to as spin up and spin down.
Orbital Shapes
Electron Configuration
Electron configuration is a shorthand
notation for describing the arrangement
of the electrons about the nucleus.
General Format using the quantum numbers:
n = principle quantum number
n l e- l = angular momentum quantum
number
RULES:
e- = number of electrons
1. Fill the lowest energy levels first.
Lowest
1s 2s 2p 3s 3p 4s 3d 4p
2. No more than two electrons per orbital.
Electron Configuration
Examples:
H : 1s1
He: 1s2
Li : 1s2 2s1
Co: 1s2 2s2 2p6 3s2 3p6 4s2 3d7
Br: 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5
The condensed electron configuration distinguishes the
core electrons from the valence electrons. CORE
electrons are tightly held to the nucleus and resemble a
noble gas configuration. VALENCE electrons are the
outer most electrons and are involved in chemical
reactions.
Examples of the condensed configuration:
Li:[He] 2s1
Co:[Ar] 4s2 3d7
2
10
5
Electron Configuration
Practice Problems
1. Give the full electron configuration:
C
O
Ne
Na
Si
Cl
Ar
K
2. Give the condensed electron configuration:
C O
Ne
Na
Si
Cl
Ar K
Answers on next slide
Electron Configuration
Answers
1 & 2. Give the full & condensed electron configuration:
C 1s2 2s2 2p2
or
[He] 2s2 2p2
O 1s2 2s2 2p4
or
[He] 2s2 2p2
Ne 1s2 2s2 2p6 or
[Ne]
Na 1s2 2s2 2p6 3s1
or [Ne] 3s1
Si 1s2 2s2 2p6 3s2 3p2 or [Ne] 3s2 3p2
Cl 1s2 2s2 2p6 3s2 3p5 or [Ne] 3s2 3p5
Ar 1s2 2s2 2p6 3s2 3p6 or [Ar]
K 1s2 2s2 2p6 3s2 3p6 4s1 or [Ar]4s1
Orbital Diagrams
RULES:
1. Aufbau Principle – electrons fill the
lowest energy level first
2. Hunds Rule – electrons fill each
orbital in a subshell with one electron
first before they double up.
3. Pauli Exclusion Principle – no two
electrons can have the same four
quantum numbers
Orbital Diagrams
4p ___
3d ___
4s ___
3p ___
3s ___
2p ___
2s ___
1s ___
___ ___
___ ___ ___ ___
___ ___
___ ___
Pauli Exclusion Principle
Hunds Rule
Aufbau Principle
Orbital Diagrams
Practice Problems
1. Draw orbital diagrams for:
C
O
Ne
Na
Si
Cl
Ar
K