Transcript Module 2 Lesson 3 Electron configuration

Electron Configuration and
Basic Quantum Model
NC Essential Standard
1.3.2
Quantum mechanics and it relation to electron configuration
Quantum Model
• The quantum model describes the probability of locating an
electron at any place.
• Heisenberg Uncertainty Principle – it is impossible to know both
the velocity (momentum) and the position of an electron at the
same time.
– The impact of a photon of light alters the motion of the electron
in unpredictable ways, so measuring position changes velocity
• Each electron is assigned four quantum numbers that describe it.
No two electrons of an atom can have the same four quantum
numbers.
Principle Energy Level, n
• Indicates main energy level occupied by e• Always a whole number (1, 2, …)
• To calculated the number of electrons that a given energy level can
have. Simpley use the formula 2n2
• 1st level can hold 2(1)2 = 2 e• 2nd level can hold 2(2)2 = 8 e• 3rd level can hold 2(3)2 = 18 e• 4th level can hold 2(4)2 = 32 e• The period indicates the # of principle energy levels
Sublevels, l
• Main energy levels are then divided into sublevels
• Indicates the shape or type of orbital
– s, p, d, f
– s sublevel is spherical and holds 2 e– p sublevel is shaped like a dumbbell and holds 6 e– d holds 10 e– f holds 14 e-
Orbitals, m
• Represents the orbital within the sublevel where the electron is
located
• Each orbital holds a pair of electrons therefore:
– 1 s orbital
– 3 p orbitals
– 5 d orbitals
– 7 f orbitals
Spin, s
• Each orbital holds 2 electrons that will always spin in opposite
directions the electrons are represented by +1/2 and -1/2. Note
arrows are used in the orbital notation for example ↑↓.
• The s orbital
is spherically
shaped.
There is one
s orbital for
each value n
= 1,2,3,…, of
the principle
number.
P Orbitals
• For each of the
values n = 3, 4, 5,…,
there are five d
orbitals. Four of the
five have similar
shapes, but differ in
orientation.
Electron Configurations
• Shows the electron arrangement in an atom, always represents the
lowest possible energies
• Aufbau Principle (German for “building up”) – electrons fill orbitals
that have the lowest energies first
Explanation of configuration
2
1s
sublevel
Energy level
Number of electrons
Practice
Write electron configurations
– Pb:
• 1s22s22p63s23p6
Note All the superscripts should add up to the
number of electrons
Electron Configurations
H: 1s1
Notice 3s2 and 3p5 add together to produce
Be: 1s2
the valence (outer most electrons) electrons
Li: 1s2 2s1
in the atom. This atom has7 valence
electrons.
Be: 1s2 2s2
B:1s2 2s2 2p1
Cl: 1s2 2s2 2p6 3s2 3p5
We just need to account for all the electrons and their
locations
• Since they fill up the lower levels first, only the last
shell (Valence) varies from the previous element’s
configuration
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Practice
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Write the electron configuration for
C
N
O
F
Ne
Na
Mg
Al
Practice
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Write the electron configuration for
C: 1s2 2s2 2p2
N: 1s2 2s2 2p3
O: 1s2 2s2 2p4
F: 1s2 2s2 2p5
Ne: 1s2 2s2 2p6
Na: 1s2 2s2 2p6 3s1
Mg: 1s2 2s2 2p6 3s2
Al: 1s2 2s2 2p6 3s2 3p1
Refer to this Periodic Table when writing
electron configurations
Shorthand Notation
• Shorthand notation uses the noble gases as a
reference point, for example
–
Na:
Number of valence electrons
/ group number
2
»[Ne]3s
Noble Gas
Highest energy
level / period
Sublevel / block
Shorthand Notation Samples
Li
[He] 2s1
He
1s2
K
[Ar] 4s1
P
[Ne] 3s2 3p3
Cl
[Ne] 3s2 3p5
Al
[Ne] 3s2 3p1
Shorthand Notation Practice
B
Ar
K
Ca
H
Mg
Shorthand Notation Practice
Answers
B
[He] 2s2
Ar
[Ne] 3s2 3p6
K
[Ar] 4s1
Ca
[Ar] 4s2
H
1s1
Mg
[Ne] 3s2
Orbital notation
• Orbital notation uses lines to represent orbits and arrows to
represent the spin of each electron.
Electron spinning
clockwise
Electron spinning counter
clockwise
1s
Energy level and sublevel
Orbital Notation
• Orbital notation uses lines to represent orbits
and arrows to represent the spin of each
electron.
• oxygen has a total of 8 eThe e- configuration for O:
1s2 2s2 2p4
Hund’s Rule: e- spread out within equivalent orbitals
↑↓
↑↓
↑↓
↑
↑
1s
2s
3s
3s
3p
Sample Orbital Notation
He
Be
N
F
Practice Orbital Notation
Practice
Element
Li
C
Al
O
Orbital Notation
Element
Li
C
Al
O
Orbital Notation
1s2 2s1
1s2 2s2 3s2 3p13p1
1s2 2s2 2p2 2p2 2p2 3s2 3p1
1s2 2s2 2p2 2p2 2p2
Mixed practice
Symbol Group# Valence
e-
[Ar]4s2
[Ne]3s23p3
[He]2s22p5
1s22s2
1s22s22p3
1s22s22p63s23p1
Period
S,p,d,f
block
Highest
energy
level
Symbol
Group#
Ca
2
2
4
s
4
[Ne]3s23p3
P
5A /15
5
3
p
3
[He]2s22p5
O
6A /16
7
2
p
4
1s22s2
Be
2
2
2
s
2
1s22s22p3
N
5A /15
5
2
p
2
1s22s22p63s23p1
Al
3A /13
3
3
p
3
[Ar]4s2
Valence Period S,p,d,f
eblock
Highest
energy
level