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Unit 2: Electron Configuration (Gen) Name: __________________
Historical Development of the Quantum Mechanical Model
Max Planck • said, “Energy is quantized.” • Quantized – the electron is limited to certain energy levels & positions
Heisenberg Uncertainty Principle • The position and momentum of the electron cannot be known at the same time. • The electron’s mass is VERY small. The act of observation changes its position.
Why do we not use Bohr’s model today? • Bohr put the electrons in very specific positions. • We are not allowed to know that much information.
The Quantum Mechanical Model • Louis de Broglie
o “wave theory” o Electrons have particle AND wave-like properties
• Probability of the electron’s location
Electron Configuration • “configuration” means “arrangement” • Describes where the electrons are located in the atom
o organized into energy level & sublevel
Part
s of
the
Qua
ntum
Mec
hanica
l Mod
el
Energy Level
• The distance the electrons are from the nucleus
• Represented by the “row number” on the periodic table
Sublevel • Area that represents the
probability of the electron’s location • Corresponds to a “block” on the
periodic table
Orbital All orbitals within a sublevel have the
same energy, but a different orientation.
• 1 orbital in an s sublevel • 3 equal-energy orbitals in a p sublevel
Electron Spin
The electron’s location can be modeled in an orbital diagram.
• Aufbau Principle – electrons are added one at a time to the lowest energy levels first
• Pauli Exclusion Principle – an orbital can hold a maximum of 2 electrons with opposite spin
• Hund’s Rule – electrons occupy equal energy orbitals singly before pairing
HISTORICAL DEVELOPMENT OF THE
QUANTUM MECHANICALMODEL
LINE SPECTRADO NOT WRITE IN NOTES!
• Different elements = different lines!• No two elements have the same line spectrum
• Like a fingerprint• Not a “rainbow” of ROYGBIV
• only certain colors
• An element’s chemical behavior (AKA its line spectrum) is related to its electron arrangement.
MAX PLANCK
• “Energy is quantized”
• Quantized – the electron is limited to certain energy levels & positions
Max Planck
• “Quantized”
A person is limited to be on a stair. The electron is limited to be in certain locations in the atom. The electron cannot float anywhere it wants, just like a person cannot float between two stairs.
HEISENBERG UNCERTAINTY PRINCIPLE
• the position and momentum of the electron cannot be known at the same time
Werner Heisenberg
Balloon is massive, so the light doesn’t change its position.
The electron is small. Observing it changes its position.
WHY DO WE NOT USE BOHR’S MODEL TODAY??
• He put the electrons in very specific positions.
• We are not allowed to know that much information.
Quantum Mechanical Model
Parts of the Quantum Mechanical Model
i. Energy Level
ii. Sublevel
iii. Orbital
iv. Electron Spin
Quantum Mechanical Model• probability of the electron’s location
• electrons are treated as waves
Who?• Louis de Broglie – “wave theory” Electrons have particle AND wave-like
properties
Why is this important?• the wave equation can be drawn as an “electron cloud”
• shows the probability of finding the electron
Energy Level
Energy Level• The distance the electrons are
from the nucleus
• Represented to the “row number” on the periodic table
Sublevel
SublevelArea that represents the probability of the electron’s location.
Increasing Energy
Sublevel
s pd
f
Corresponds to a block on the periodic table
Corresponds to a block on the periodic table
How to Write Electron Configuration
Electron Configuration• Describes where the electrons are located in the atom
• “Configuration” means “arrangement”
Electron Configuration• Where an atom’s electrons are distributed Organized into energy level, sublevel, & orbitals
Energy level Sublevel
Quantity of electrons
Energy arrangement of the “d” sublevel
Energy arrangement of the “d” sublevel
Orbital
OrbitalIf one “s” or “p” or “d” or “f” can hold 2 electrons, then how many do you need to contain all the possible electrons?
OrbitalAll orbitals within a sublevel have the same energy,
but a different orientation.
Electron Spin
3 Rules of Electrons in Orbitals
• Aufbau Principle – electrons are added one at a time to the lowest energy levels first
• Pauli Exclusion Principle – an orbital can hold a maximum of 2 electrons with opposite spin
• Hund’s Rule – electrons occupy equal energy orbitals singly before pairing
Orbital Diagrams
Orbital Diagram• A way of showing how electrons fill orbitals
• Electrons are represented by an “arrow”
3s
2p
2s
1s
Orbital Box DiagramAccording to the Pauli Exclusion Principle…
• Put 2 arrows in each box maximum
• Arrows in opposite directions to represent spin
3s
2p
2s
1s
Orbital Box DiagramAccording to Aufbau Principle…
• Start at bottom, not top
3s
2p
2s
1s
Orbital Box DiagramAccording to Hund…
• Put arrows in one at a time before pairing them up
3s
2p
2s
1s
Orbital Box DiagramAccording to Hund…
• Put arrows in one at a time before pairing them up
3s
2p
2s
1s
Orbital Box DiagramAccording to Hund…
• Put arrows in one at a time before pairing them up
3s
2p
2s
1s
Orbital Box DiagramAccording to Hund…
• Put arrows in one at a time before pairing them up
3s
2p
2s
1s
Orbital Box DiagramAccording to Hund…
• Put arrows in one at a time before pairing them up
3s
2p
2s
1s
Orbital Box DiagramAccording to Hund…
• Put arrows in one at a time before pairing them up
3s
2p
2s
1s
Orbital Box DiagramAccording to Hund…
• Put arrows in one at a time before pairing them up
3s
2p
2s
1s
Orbital Box DiagramAccording to Hund…
• Put arrows in one at a time before pairing them up
3s
2p
2s
1s
Orbital Box DiagramAccording to Hund…
• Put arrows in one at a time before pairing them up
3s
2p
2s
1s
Orbital Box DiagramAccording to Hund…
• Put arrows in one at a time before pairing them up
3s
2p
2s
1s
Orbital Box DiagramAccording to Hund…
• Put arrows in one at a time before pairing them up
3s
2p
2s
1s
Orbital Box DiagramAccording to Hund…
• Put arrows in one at a time before pairing them up
3s
2p
2s
1s
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