Compounds

Video Clip: Why it Matters

NOTES 2: VALENCE ELECTRONS, LEWIS DOT DIAGRAMS, AND OXIDATION NUMBERS

1. How many total electrons are in a neutral atom of Sulfur?

2. How many electrons are in sulfur’s highest energy level (it’s most outer shell)(HINT: use the picture to the right)?

Review: Bohr’s Electron Model

3. How many electrons does sulfur need to gain or lose in order to have 8 valence electrons (electrons in the outermost shell)?

Bohr developed an atomic model in which the electrons are arranged in specific energy levels.

The lowest level (n=1) is located closest to the nucleus. The highest level is located farther away from the nucleus.

Recap: Bohr’s Electron Model

*The electrons in the highest energy level for any element are

known as valence electrons.*

Valence electrons are involved in chemical bonding.

Bonding and Valence Electrons Video Clip

Recap: Bohr’s Electron Model

Valence Electrons:

Valence Electrons can be easily found by looking at the Group number or “A” number located above the column where the element is located on the periodic

table.

 

Examples:

Al= Group # ___ and ____A so it has ___ valence electrons.

 

Pb= Group # ___ and ____ A so it has ____ valence electrons.

 

13 3 3

14 44

Valence Electrons the Quick and Easy Way

Determine the number of valence electrons.

PhosphorusArgonLeadBarium

5 valence electrons

8 valence electrons

4 valence electrons

2 valence electrons

Exceptions• * This ONLY works for Group A Elements (the Representative Elements)

• Helium two valence electrons

LEWIS DOT DIAGRAMS: is a diagram in which the chemical symbol of an element represents the nucleus and the inner energy level and “dots” represent the valence electrons.

1. There can only be up to 8 valence electrons and thus only 8 dots around a symbol.

2. The first 4 dots are single and then they pair up as more are added.

Octet rule states that all atoms wish to be like the Nobel gases (group 18) with a full valence of 8 electrons.

Lewis Dot Diagrams

Element Symbol

One Dot for Each Valence

Electron

How Are the Dots Arranged?

X1

2

3

4

5

6

7

8

Example Dot DiagramsDraw the dot diagrams for each of the following elements.

•Helium

•Carbon

•Fluorine

•NeonHe F

C Ne

Oxidation numbersOXIDATION NUMBERS: is the number of electrons an atom gains, loses, or shares when it forms a chemical bond and achieves the octet rule.

This will also be the charge of the ION.

Metals as a rule lose electrons and will have a (+) charge. Nonmetals will gain electrons and have a ( -) chargeNobel gases in group 18 will not lose or gain and have a 0 charge

Color your metals and non-metals with two different colors.

0 0

4 4 +-4

7 -1

8 00

Complete homeworkpage 6