Chapter 5: Electrons in Atoms Section 2:Electron Arrangement in Atoms
Apply the aufbau principle, the Pauli exclusion principle, and Hund’s Rule to generate electron configurations and spin diagrams; Explain that there can be exceptions to the normal rules for electron configurations; and Draw modified Bohr diagrams for atoms Student will be able to:
Electron’s address Energy level Sublevel Orbital Spin Where do electrons live?
Need a system for electron addresses...
Energy levels are numbered(1, 2, 3...) Each energy level adds one more sublevel (letters) Each sublevel adds two more orbitals Sublevels and orbitals
Sublevels addressed by the number of their energy level and letter of sublevel Example: 1s, 2s, 2p, 3s, 3p, 3d Still two more parts to address (orbital and spin)... Electron configuration: arrangement of electrons in an atom in its ground state Orbital diagram: illustrates arrangement and spin of electrons Keeping track of all the sublevels
Aufbau principle: electrons occupy orbitals of lowest energy first Electrons (like some students) are lazy Orbitals in same sublevel are same energy Rules for Electron Configurations
Pauli Exclusion Principle Orbital can hold maximum of two electrons (Two per seat on the bus) If two electrons in an orbital, must be opposite spins Two possible spins: up and down Rules for Electron Configurations
Hunds Rule Orbitalsin same sublevel are same energy Electrons fill orbitals of same energy so they maximize same spin Students don’t pair up in a seat until they have to Rules for electron configurations
One electron for every proton Periodic table arranged by atomic number Typewriter method: start at H, read left to right, and stop at the element you’re configuring Putting the rules to use...
Further down the table... La starts 4f sublevel Comes after 6s and before 5d Lu is actually 5d1 Ac starts 5f sublevel Comes after 7s and before 6d Lr is actually 6d1 Try some...
There are exceptions to the normal rules for electron configurations Based on stability Just know that they exist, not how to do them Just when you learn the rules...
Atom drawn with nucleus in center and one ring for each energy level Electrons drawn as dots on the rings Example: S 1s2, one ring, 2 dots 2s2, 2p6, one ring, 8 dots 3s2, 3p4, one ring, 6 dots Bohr Diagrams
Group electrons by sublevels Show spins Example: S 1s2 one ring, 2 arrows paired 2s2, 2p6 one ring, 2 arrows paired (s), 6 arrows paired (p) 3s2, 3p4 One ring, two arrows paired (s) four arrows with two paired (p) “Modified” Bohr Diagrams 16 p 16n
Apply the aufbau principle, the Pauli exclusion principle, and Hund’s Rule to generate electron configurations and spin diagrams? Explain that there can be exceptions to the normal rules for electron configurations? Draw modified Bohr diagrams for atoms? Can you…?