# 8 th Grade Physical Science Bohr Model & Lewis Dot Diagrams.

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8 th Grade Physical Science Bohr Model & Lewis Dot Diagrams

Recall...

Atom Diagrams There are two models of the atoms we will be using in class. Bohr Model Lewis Dot Structure

Bohr Model The Bohr Model shows all of the particles in the atom. In the center are circles. Each circle represents a single neutron or proton. Protons should have a plus or P written on them. Neutrons should be blank or have an N. In a circle around the nucleus are the electrons. Electrons should have a minus sign or an e.

Facts: You can’t just shove all of the electrons into the first orbit of an atom. Electrons orbit the nucleus in energy levels, shells, we even call them electron clouds or orbitals. Only so many electrons can be in any certain shell. The electrons in the outer most shell of any element are called valance electrons.

Row ## of Elements in the Row Maximum # of Electrons for that Energy Level Valence 122# of electrons in outermost shell 288 388

Atomic Structure

Try an Example! How to draw a Lithium atom… First, look at the Periodic Table of Elements Second, determine the number of protons (atomic number) Then determine the number of neutrons (atomic mass – atomic number) Then determine the number of electrons (atomic number)

Practice: Try the following elements on your own: a) H b) O c) Al

Lewis Dot Diagrams The Lewis Dot Structure is a bit different from the Bohr model. It only shows the element symbol and it’s outer most electron shell.

Example: Step 1: Write the Element Symbol Step 2: Find the number of electrons in the last energy level of the Bohr Model (Valence Electrons) Step 3: Place the electrons (dots) around the symbol in clockwise order so that there are no more than 2 electrons per side. Practice: Lithium