Metal atoms lose e- to form positive ions called cations:

K+

Ca 2+

NH4+

Nonmetal atoms gain e- to form negative ions called anions:

Cl-

S2-

CO32-

Mg2+

Superscript written to the upper right shows the charge

F-

If the charge is +1 or -1, you don’t have to include the “1”

Called an “oxidation number”

Ion: An atom (or group of atoms) that has lost or gained e- to follow the Octet Rule and is now electrically charged

IonizationF + e- F-

Neutral but unstable fluorine atom, F

Write the (oxidation) equation showing how magnesium becomes an ion

Same # electrons as neon, but NOT an atom of neon!

Mg Mg2+ + 2e-

Same # e- as…which element?

Write the (reduction) equation showing how flourine becomes an ion

1A metals: +1 ions 2A metals: +2 ions

7A nonmetals: -1 ions 6A nonmetals: -2 ions

What patterns do you see? Are there any exceptions to

these patterns?

Nonmetal atoms remove e- from metal atoms.

Ionic Bonds

The two atoms become oppositely charged ions that attract each other, resulting in an ionic bond. An ionic compound forms.

Na+

Cl-

EX 2: Write the formula for the ionic compound calcium oxideStep 1: Write each ion with the correct charge. Look at periodic table group or cheat sheet for help. Ca2+ O2-

Step 2: “Criss-cross” number associated with each charge (do not include the + or -) Ca2O2

Step 3: Remove any subscripts of 1. Eliminate both subscripts if they are the same. Write the formula.CaO

EX 3: Write the formula for the ionic compound aluminum Sulfide

Al3+ S2-

Al2S3

Name Formula

potassium nitride

Magnesium bromide

potassium phosphide

magnesium fluoride

K3N

MgBr2

K3P

MgF2

Name these 2 compounds:CoSa.Figure out which ions

form the compound because the ion charge could be important.

Since S forms S2-, Co must be Co2+

b. Name the ions, cation first, then anion

c. Change ending to –ide if it’s a pure element.

cobalt (II)sulfide

d. Transition metals always get a roman numeral to indicate their charge!

Na2SO3

sodium sulfiteCommon mistakes:sodium(II)sulfitesodium(I)sulfitesodium sulfide/sulfate

Formula NameNa2O

SrS

LiBr

RbCl

Sodium Oxide

Strontium Sulfide

Lithium Bromide

Rubidium Chloride