# Valence Electrons & Bohr Diagrams

Valence Electrons & Bohr Diagrams Review: Atomic Structure Atoms have a nucleus that contains Protons and Neutrons Electrons are contained in shells that surround the nucleus An atom is made of mostly empty space Protons have a positive charge Electrons have a negative charge Neutrons are Neutral Review: Electrons & Shells

Each electron shell can hold a certain number of electrons Electron shells are filled from the inside out Noble Gases have full outer electron shells All other elements have partially filled outer electron shells Electron Shell

Number of Electrons 1 2 2 8 3 8

4 18 5 18 6 32 7

32 Valence Electrons The electrons in the outer most electron shell are called valence electrons The shell containing electrons that is furthest from the nucleus is called the valence shell The number of electron shells with electrons is the same as the period (row) number Noble Gas Stability

Noble gases (column all the way to the right) are usually unreactive This is because they have full valence shells (a stable octet) An element with a full valence shell is a happy element All elements are trying to get a stable octet! Noble Gas Stability Atoms want to gain stability Atoms will try to gain or lose electrons to have a full valence shell

Bohr Models Niels Bohr created a visual model of the atom to make them easy to understand A Bohr Model contains a central nucleus surrounded by electron shells For each model you state the number of protons and neutrons in the nucleus and draw a dot on the electron shells for each electron To determine the number of valence electrons an element has, you look at the number of electrons in the outermost shell Complete the Bohr Model of the Atom

Arranging Electrons in Energy Levels in your Notebook. For the second half when you are coloring the electrons, remember, you wont use every circle on every shell it depends on how many electrons the element has. For example, Sodium has 11 electrons, so you will only use 11 circles.

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