Lewis Dot Structures

Aka Dot Diagrams

Electron Dot Diagrams

Valence electrons are the electrons on the

outermost energy level.

Image from Wikipedia

6 valence electrons on this atom.

The final s and p valence electrons are especially important because they determine

what kinds of reactions an atom will undergo.

1s 2s 2p

Valence electrons

If you write the Shorthand Configuration for an element, the s and p electrons on the highest energy level are the

valence electrons.

Example: Tin, Sn:

1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p2

vale

nce

elec

trons

Lewis Dot Structures show only the Valence electrons for an element. • A Dot Diagram

consists of two parts:

– the element symbol – dots that represent

the S and P block electrons

Dots may only go on the sides of the element

symbol

Sn

Rules for Writing Lewis Dot Diagrams:

• Only use s and p valence electrons

• If there are d or f valence electrons in between the s and p sublevels, they are left out of the dot diagram.

1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p2

Rules for Writing Lewis Dot Diagrams:

• You must put 1 electron dot on each side of the element symbol before you put 2 on one side (like Hund’s rule)

ElEl

For example: Imaginary Elementium (El) has 3 valence electrons (5s2 and 5p1)

Example: Tin, the last electrons are 5s2 4d10 5p2.

For the dot diagram, we will use only the valence electrons 5s2 and 5p2.

Therefore we will place 4 dots around the element symbol.

Sn

= places where electrons can go

Don’t draw it, just think it

Example: Bromine

Shorthand Configuration is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5.

Use only the 4s2 and the 4p5.

A total of 7 electron dots.

Br

Practice problems

• Neon

• Sodium

• Aluminum

Ne

Answers to Practice

Na

Al

No, it does not matter which side has no electron dots as long as there are the correct number of sides without dots.

Assignment

• Complete the Dot Diagram Periodic Table Assignment.

• Answer all questions.

• Be sure to label your Dot Diagram Periodic Table when the instructions say to.

• You will turn them in next week (Tuesday)