Do Now

Label the following as element or compound: Mg O2

H2SO4

FIFind the number of atoms in the following

elements/compounds: Mg O2

H2SO4

FI

The Octet Rule

Key Point #1: The octet rule says that atoms are most stable (happy) when they have 8 valence electrons

The Octet Rule - Review

We’ve talked about ions before – how atoms will gain or lose electrons in order to get eight valence electrons

An atom that has gained an electron has a negative charge

An atom that has lost an electron has a positive charge

Key Point #2: Copy the chart on the board

This chart is an easy reference to see what type of ion an element will form

But why?

Key Point #3: For atoms in groups 1, 2 and 13, it is easier to lose electrons. For atoms in groups 14, 15, 16, and 17, it is easier to gain electrons.

Why do I need to review this information on ions?

So we can predict how atoms will bond together.

Watch this…

Just in time for Halloween!

There is a TRICK to figure out what the ionic compound between a metal and a nonmetal will be.

Kris Kross Method!

Ca3As2

Ca2+As3-

Key Point #4: Kriss Kross Method: Write down the stable ions and cross the

charges to make them subscripts

Na1+Cl1-

NaClLi1+O2- Li2O

Use the charges:

Group 1 2 13

14

15

16

17

18

Charge

1+

2+

3+

4- 3- 2- 1- 0

Which charge ALWAYS

comes first?POSITIVE!!

Guided Practice

WHITEBOARDS!

I will put a problem on the board. On your whiteboard, use the KRISS KROSS method to determine the compound

K F Ba N Ga O Ca Cl K Si Co I

K1+F1- Ba N Ga O Ca Cl K Si Co I

KF Ba N Ga O Ca Cl K Si Co I

KF Ba2+N3- Ga O Ca Cl K Si Co I

KF Ba3N2 Ga O Ca Cl K Si Co I

KF Ba3N2 Ga3+O2- Ca Cl K Si Co I

KF Ba3N2 Ga2O3 Ca Cl K Si Co I

KF Ba3N2 Ga2O3 Ca2+Cl1- K Si Co I

KF Ba3N2 Ga2O3 CaCl2

K Si Co I

KF Ba3N2 Ga2O3 CaCl2

K1+Si4- Co I

KF Ba3N2 Ga2O3 CaCl2

K4Si Co I

K F Ba N Ga O Ca Cl K Si Co I

You don’t know about transition metals! So.. the problem must tell you the

number of electrons. Cobalt (II) means that Cobalt gives

up 2 electrons

K F Ba N Ga O Ca Cl K Si Co2+I1-

K F Ba N Ga O Ca Cl K Si CoI2

Independent Practice

Room should be silent during independent practice

1. For each pair find the STABLE ION2. Kris Kross!A. Mg OB. Na BrC. Rb PD. Be FE. Ca S

Exit Slip

1. For each pair find the STABLE ION2. Kris Kross!A. K ClB. Li NC. Ca O

Homework! Writing formulas worksheet. Use the KRISS KROSS method to complete

Due tomorrow