CHM 101 1st Edition Lecture 16Lecture 14 OverviewI. The Wave Behavior of MatterII. Quantum MechanicsIII. Schrodinger’s ModelLecture 15 Overview1. Electron Spin2. Pauli Exclusion Principle3. Energy Levels4. Aufbau Principle5. Electron ConfigurationsElectron Spin- In addition to the 3 quantum numbers that describe an orbital there is a 4th quantum number for electron spin- Ms describes the magnetic properties of an electron- Two possible values o Ms = +1/2 or ms = -1/2o “spin up” or “spin down”Pauli Exclusion Principle- No two electrons in an atom can have the same four quantum numbers - Because there are only two possible values for spin, an orbital can contain no more than two electrons and they must have opposite spinsEnergy Levels - In a hydrogen atom orbitals with the same value of n have the same energy- In atoms with more than one electron orbitals with the same values of both n and l have the same energy- Orbitals with the same energy are said to be degenerate- Electrons are denoted in energy level diagrams with arrows indicating the two directions of spin- Electrons will fill up the orbitals in order from lowest energy to highest energyHund’s Rule- The lowest energy arrangement of electrons in the same subshell has the max number of unpaired electrons with the same spin.Hund’s Rule:When you have an orbital above a s you fill up the squares with the same spin until you get to the last one then go back and fill in the opposite spin.Electron Configurations The exponents represent the number of electrons in that orbital, the number in front of the letter represents n, and the letter represents lCondensed NotationsExample Line Notation Condensed Line Notation - Na – 1s22s22p63s1(Ne) 3s1In order to get the condensed line notation you go back on the periodic table to the closest Noble Gas to the element, then you write down the Noble Gas and the last orbital that matches the element in
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