HMSA Welcome Back! Today in Class: Midterm Corrections (up to a 90)—whatever you get done today is what I will grade! Atoms/Nuclear Packet Atoms & Nuclear Review/Practice Packet due FRI 1/22

Review: Bohr Model of the Atom Electrons are shown in concentric shells or energy levels around the nucleus The 1st shell can hold up to 2 electrons The 2nd shell can hold up to 8 electrons The 3rd shell can hold up to 18 electrons The 4th shell can hold up to 32 electrons When filling electrons, you fill the first (inner) shell first

Electrons Valence electrons= electrons in the outermost shell of the atom

Lewis Structures (Electron Dot Diagrams) A Lewis structure is in a sense a shortcut for representing the structure of an atom. A Lewis structure contains 2 parts 1. element symbol (representing the nucleus) 2. electron dots (representing the valence electrons)

Lewis Structure Example N has 5 valence electrons, so it’s Lewis structure would look like: Maximum 2 electrons per side! Note: by convention, you should not have more than 2 electrons per “side” The maximum number of valence electrons you can have is 8.

Practice and Review Use the example to help you fill out the Bohr Diagrams, Electron Configuration, and Valence Electrons