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Electron Configurations
Electron Configurations
• Electron Configurations – the way electrons are arranged (placed) around the nucleusnucleus.
• Guiding Principle: electrons are arranged in a way that gives the lowest lowest energy to the atom. (low energy = high stability)
Rules for Electron Configurations
• Aufbau Principle – lowest lowest energy levels fill first.• Pauli Exclusion Principle – no two electrons in an atom
can be at the samesame place at the samesame time. All atomic orbitals can only hold 2 electrons maximum & they have to be spinning opposite directions.
• Hund’s Rule – Don’t pair until you have to.Don’t pair until you have to. When electrons can go into orbitals of equal energy (ex.3 types of p orbitals) one electron enters each orbital until each has one electron. They all spin the same direction until they pair up.
• Each orbital corresponds to a specific sectionsection on the periodic table.
How orbitals align on the Periodic Table
Drawing Orbital Box Diagrams
You try a few!
• Nitrogen
• Chlorine
1s2 2s2 2p3
3s2 3p51s2 2s2 2p6
Write the electron configurations for the following elements:
• Hydrogen• Helium• Lithium• Beryllium• Boron• Fluorine• Sodium• Phosphorus
1s1s11
1s1s22
1s1s222s2s11
1s1s222s2s22
1s1s222s2s222p2p11
1s1s222s2s222p2p55
1s1s222s2s222p2p663s3s11
1s1s222s2s222p2p663s3s223p3p33
Using the “d” orbitals
• The transition metals use the “d” orbitals to denote their electron configurations.
• “d” orbitals have a higherhigher energy level than “s” orbitals with a larger number. Therefore, the “s” orbital will fill before the “d” orbital.
• There are exceptionsexceptions to the rule within the transition elements.
Examples
• Scandium
1s1s222s2s222p2p663s3s223p3p664s4s223d3d11
• Titanium
1s1s222s2s222p2p663s3s223p3p664s4s223d3d22
• Vanadium
1s1s222s2s222p2p663s3s223p3p664s4s223d3d33
You try a few!
• Iron
• Nickel
• Bromine
1s1s222s2s222p2p663s3s223p3p664s4s223d3d66
1s1s222s2s222p2p663s3s223p3p664s4s223d3d88
1s1s222s2s222p2p663s3s223p3p664s4s223d3d10104p4p55
Using the “Core” to shorten things up:
• Instead of writing the entire electron configuration, you can use the “core”“core” of the last noble gas.
• Example: Phosphorous
Regular - 1s1s222s2s222p2p663s3s223p3p33
Core - [Ne] 3s3s223p3p33
You try!
Chlorine
Barium
Iodine
[Ne] 3s[Ne] 3s223p3p55
[Xe] 6s[Xe] 6s22
[Kr] 5s[Kr] 5s224d4d10105p5p55
What is the most common college mascot in the NCAA?
Bulldogs – shared by 13 teams
2nd – Tigers
3rd – Bears
4th- Wildcats