# Chapter 13 Electrons Models of the Atom Electron Arrangement Physics and the Quantum Mechanical Model.

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Chapter 13 Electrons Models of the Atom Electron Arrangement Physics and the Quantum Mechanical Model

Chapter 13.1 Models of the Atom The atom was considered a solid indivisible mass originally http://www.youtube.com/watch?v=uhgd9VM9rsM

Thomson Model Plum – Pudding Atom: Negatively charged electrons stuck into a lump of positively charged material.

Rutherford Model Electrons surround a dense nucleus made of protons and neutrons. The rest of the atom was empty space

Bohr Model (Planetary Model) Electrons are arranged in concentric circular paths (orbits) around the nucleus. Patterned after the motion of the planets Electrons have a fixed energy

Quantum Mechanical Model Primarily a mathematical model Restricts electron to certain energy levels No defined path for electrons Gives a percent chance of finding an electron in a certain space

Quantum Amount of energy required to move an electron from its current energy level to the next highest energy level

Fixed Energy Levels Rungs of a Ladder Garden Steps

Orbits S orbital P orbital D orbital F orbital

Chapter 13.2 Electron Arrangement Electron Configurations Exceptional Electron Configurations

Electron Configurations The way in which electrons are arranged around the nuclei of an atom. Three Rules: –Aufbau Principle –The Pauli Exclusion Principle –Hund’s Rule

Aufbau Principle Electrons enter orbitals of lowest energy first. Some orbitals overlap between different energy levels

The Pauli Exclusion Principle An atomic orbital may describe at most two electrons One or two electrons may occupy one orbital They will have opposite spins (shown by opposite arrows)

Hund’s Rule When electrons occupy orbitals of equal energy, one electron enters each orbital until all the orbitals contain one electron with parallel spins.

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