University:
Felician University
Course:
CHEM-001 | Basic Chemistry
Academic year:

2024
Views:

402

Pages:

18
Author:

Clint W.

Electron Configurations And Orbital Diagrams Principles for Filling Orbitals Writing electron configurations – Aufbau principle Higher energy • Electrons are added one at a time to the lowest energy levels available until all the electrons have been accounted for – • 2 electrons per orbital Carbon: 1s2 2s2 2p2 (up to 6 electrons can fit in a psublevel, 2 in each of 3 orbitals ) 7s 7p 7d 7f 6s 6p 6d 6f 5s 5p 5d 5f 4s 4p 4d 4f 3s 3p 3d 2s 2p 1s Lower energy The Periodic Table and Predicted Orbital Configurations Another way to show an Aufbau diagram: Two Other Rules for Filling Orbitals: • Pauli Exclusion Principle - Electrons must have opposite spins to occupy the same orbital. • Hund’s Rule: Orbitals must be filled in a way that gives the maximum number of unpaired electrons. – By placing electrons in different orbitals, electronelectron repulsions are minimized. Using Hund’s Rule and the Pauli Exclusion Principle 2 mistakes Orbital Diagrams Lithium Beryllium Boron Carbon Nitrogen Neon Sodium What is wrong with these? Abbreviated Electron Configurations • Highlights Valence electrons • The preceding noble gas symbol in brackets followed by the rest of the configuration. For Example: Sodium [Ne] 3s1 Fluorine [He} 2s2 2p5 Electronic Classification • Core e-: complete the previously filled noble gas • Valence e-: are in the highest energy level outside the noble gas core. Involved in bonding. • Pseudo-valence e- : are outside the noble gas core in lower energy levels – contribute to shielding – occasionally take part in bonding 14 Unpaired Electrons • Unpaired electrons are important. • If an element has unpaired electrons, it is paramagnetic and attracts a magnet. • If an element has no unpaired electrons it is diamagnetic and does not attract a magnet. Exceptions to the electronic configurations Following the rules for Cr, Cu, Ag, and Au using noble gas notation we expect the following: Element Expected Experimental Cr Cu Ag Au [Ar] 3d4 4s2 [Ar] 3d9 4s2 [Kr] 4d9 5s2 [Xe] 5d9 6s2 17 [Ar] 3d5 4s1 [Ar] 3d10 4s1 [Kr] 4d10 5s1 [Xe] 5d10 6s1