Catalyst: 10.27.2008Find the atomic #, mass #, # protons, #

electrons, and # neutrons for the following elements:

Beryllium & Lithium

Objective

Explain how electrons are placed in the electron cloud.

Identify valence electrons

Make atomic diagrams with proper electrons

Construct Lewis Dot Diagrams to show valence electrons

Electron Energy Levels & Lewis Dot Diagrams – 10.25.2008

Electron Location

Where are electrons located in an atom?

Outer electron cloud

What do they do there?

Constantly moving

How are they arranged in the electron cloud?

In a specific pattern called energy shells (or levels)

Electron Energy Levels & Lewis Dot Diagrams – 10.25.2008

Electron Location

-e- constantly moving & found in electron cloud- arranged in energy shells/levels

Energy Shells

Each shell or level has a specific amount of energy (E)

Each shell can only hold a certain amount of electrons.

Electron Energy Levels & Lewis Dot Diagrams – 10.25.2008

Electron Location

Energy Shells/Levels

-e- constantly moving & found in electron cloud- arranged in energy shells/levels

- each level has specific amt. of energy

Energy Shells

Each energy shell/level is represented by a circle around the nucleus of the atom.

The first (lowest) energy level holds only 2 electrons

After this level is filled up,electrons go to a higher (outer) E level.

Electrons fill the lower levels andthen move to higher (outer) levels.

Electron Energy Levels & Lewis Dot Diagrams – 10.25.2008

Electron Location

Energy Shells/Levels

-e- constantly moving & found in electron cloud- arranged in energy shells/levels

- each level has specific amt. of energy- 1st energy level: 2 e- maximum- after a level is filled up, e- go to higher (outer) energy levels

Energy Shells

No matter how many energy levels there are, the outermost energy level can only hold at most 8 electrons

The outermost energy level is called the valence shell.

Electron Energy Levels & Lewis Dot Diagrams – 10.25.2008

Electron Location

Energy Shells/Levels

-e- constantly moving & found in electron cloud- arranged in energy shells/levels

- each level has specific amt. of energy- 1st energy level: 2 e- maximum- after a level is filled up, e- go to higher (outer) energy levels- valence shell – outermost energy level / can hold @ most 8 e-

Energy Shell Example (Left page)

Carbon: What is its symbol? What is the atomic number? What is the atomic mass? How many protons does it have? How many electrons does it have? How many neutrons does it have? How many electrons go in the first shell? How many electrons go in the next shell? How many valence electrons are there?

Energy Shell Example (Left page)

Carbon: What is its symbol? C What is the atomic number? 6 What is the atomic mass? 12 How many protons does it have? How many electrons does it have? How many neutrons does it have? How many electrons go in the first shell? How many electrons go in the next shell? How many valence electrons are there?

Energy Shell Example (Left page)

Carbon: What is its symbol? C What is the atomic number? 6 What is the atomic mass? 12 How many protons does it have? 6 How many electrons does it have? 6 How many neutrons does it have? How many electrons go in the first shell? How many electrons go in the next shell? How many valence electrons are there?

Energy Shell Example (Left page)

Carbon: What is its symbol? C What is the atomic number? 6 What is the atomic mass? 12 How many protons does it have? 6 How many electrons does it have? 6 How many neutrons does it have? 6 How many electrons go in the first shell? 2 How many electrons go in the next shell? 4 How many valence electrons are there? 4

Energy Shell Example (Left page)

Carbon: What is its symbol? C What is the atomic number? 6 What is the atomic mass? 12 How many protons does it have? 6 How many electrons does it have? 6 How many neutrons does it have? 6 How many electrons go in the first shell? 2 How many electrons go in the next shell? 4 How many valence electrons are there? 4

Energy Shell Example #2 (Left page)

Draw an atomic diagram for Helium.

How many valence electrons are there in Helium?

Energy Shell Example #2 (Left page)

Draw an atomic diagram for Helium.

How many valence electrons are there in Helium?

2e-

2 p+

2 n0

e-

e-

Lewis Dot Diagrams

Lewis Dot Diagrams are a way to show you how many valence electrons are in an atom.

How many valence electrons were in Carbon?

4 valence e-

Lewis Dot Diagram of Carbon:

Electron Energy Levels & Lewis Dot Diagrams – 10.25.2008

Lewis Dot Diagram

-Show how many valence electrons in an atom.-

Lewis Dot Diagram Practice (Left Side)

Draw the Lewis Dot Diagram for each of the following:1. Element X has 2 valence electrons.2. Element Y has 5 valence electrons.3. Element Z has 7 valence electrons.

Practice Problems

You will create an atomic diagram with correct number of energy levels AND a Lewis Dot diagram for each of the of following elements:

Boron, Nitrogen, Phosphorous, Chlorine, and Fluorine.

2 p+

2 n0

e-

e-