Rule of eight

The Octet rule of bonding

Unit 1 • Investigation V

ChemCatalyst

– Only certain combinations of elements result in the formation of compounds.

– Li, lithium, will react with F, fluorine, to form LiF, but it won’t form LiF2 or LiF3.

– Mg, magnesium will react with F to form MgF2, but it won’t form MgF or MgF3.

– Explain what you think is going on.

Unit 1 • Investigation V

The Big Question

– What determines how two elements will combine to a stable compound?

Unit 1 • Investigation V

– Octet Rule: Ionic compounds tend to form from atoms that together have a total of 8 (or a multiple of 8) electrons in their outermost (valence) shells. This gives each ion a valence electron configuration identical to a noble gas and makes them very stable.

– 2nd requirement: There must be at least 1 cation and 1 anion in each compound

Rule of eight

AL2O3

Handout instructions

1) Name on handout

2) Fill out all empty spaces in chart (valence electrons, Compound formula)

3) Write Cation, Anion name (Noble gas configuration) in 1st and 3rd columns

Unit 1 • Investigation V

ActivityElement 1

(metal, cation)

# of valence

electrons

Element 2(nonmetal,

anion)

# of valence

electrons

compound total # of valence

electrons

Na 1 F 7 NaF sodium fluoride

8

Mg O MgOmagnesium

oxide

Mg 2 Cl 7 MgCl2magnesium

chloride

16

Ne Neneon

Be F BeF2

beryllium fluoride

Unit 1 • Investigation V

Element 1(metal, cation)

# of valence

electrons

Element 2(nonmetal,

anion)

# of valence

electrons

compound total # of valence

electrons

MgSmagnesium

sulfide

CaCl2calcium chloride

Na Br

K Se

Al N

Al O Al2O3

aluminum oxide

Al F

Unit 1 • Investigation V

Check-In

– What elements will combine with Sr, strontium, in a one-to-one ratio?

Unit 1 • Investigation V

Wrap-Up– Elements react to form compounds in

such a way as to result in 8 electrons in their outermost (valence) shell (or a multiple of eight).

– Compounds with eight valence electrons are very stable.

– Noble gases already have eight valence electrons and don’t combine with other elements to make new compounds. They are already very stable.

Second part of lab

Octet Rule and its use in forming compunds

QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.

DISTRIBUTE THE SALTY EIGHT CARDS

Discuss information shown on the card

Definition of a salt

• An ionic compound formed by acting a acid with a base

• Examples include NaCl, KCl, CuSO4

Unit 1 • Investigation V

ChemCatalyst – List the compounds you can make with

pairs of cards of two different elements.– List the compounds you can make with

three cards and only two different elements.

Unit 1 • Investigation V

The Big Question

– What salts can be formed by combining a metal and a non-metal?

Unit 1 • Investigation V

You will be able to:

– Apply the octet rule.

Procedure

• Divide up into groups of 4

• Get a deck of salty eight cards

• Play game

Unit 1 • Investigation V

Activity• Rules for Salty Eights:• The point of the game is to make

compounds and to be the first to play all of the cards in your hand. These compounds can have two or three or more cards in them, but they can only have two different elements. The game ends when a player uses up all of the cards in his or her hand making compounds.

(cont.)

Unit 1 • Investigation V

– Shuffle the deck as best as possible.– Deal eight cards to each player.– The player to the left of the dealer plays

first. – Using at least two cards from your hand,

try to make one compound – the valence electrons must add up to eight or a multiple of eight. You must have at least one pink card and one blue card with each compound noble gases—green cards—are an exception and can be played singly

(cont.)

(Game Sequence)

Unit 1 • Investigation V

– You must play every turn. In other words you must make one compound each time it is your turn. If you cannot make a compound you must draw from the draw pile until you can put down a compound.

– When you form a compound during your turn simply place those cards on the table in front of you.

(cont.)

(cont.)

Unit 1 • Investigation V

– Play proceeds around the circle until a player uses up all of his or her cards.

– A player gets 20 points for going out first.

– Wild cards can be used as any element in that particular group (Wild cards only exist for Groups 1 and 7). The player must identify which element a wild card represents at the time it is played. (cont.)

(cont.)

Card/Play Values

Card/ Card Combination/ Play option Point value

Place a noble gas card 5 points

Form a compound out of 2 cards 10 points

Form a compound out of 3 cards 40 points

Form a compound out of 4 cards 70 points

Form a compound out of 5 cards 100 points

Going out first (have formed compounds with all cards) 20 points

Unit 1 • Investigation V

• Scoring:

• Every compound played on the table is worth points. The cards left in a person’s hand are subtracted.

• Any player with cards left in his or her hand must count up the number of valence electrons and subtract them from his or her total.

(cont.)

Scoring

Unit 1 • Investigation V

Metal

Cation

Nonmetal

Anion

Compound

Formula

Compound

Name

Point

value

Total

Tournament time

Must complete chart as proof

Unit 1 • Investigation V

Check-In

• Which of the following compounds are likely to form?

• (a) Na2S• (b) K2Mg • (c) AlBr2

• (d) Na3N• (e) OCl• (f) CaMgO2

Unit 1 • Investigation V

Wrap-Up– Ionic compounds tend to form from

atoms that together have a total of 8 (or a multiple of 8) electrons in their outermost (valence) shells

– Compounds with eight valence electrons are highly stable.

– Noble gases already have eight valence electrons and don’t combine with other elements to make new compounds. They are already highly stable.