Write the electron configuration for K and Br.

Circle the Valence Electrons

A John Modica Production

Ionic Compounds

• Because electrons are negatively charged…– an atom becomes positively or negatively

charged as it loses or gains an electron, respectively.

• Any atom or group of atoms with a net charge (whether positive or negative) is called an ion.

• A positively charged ion is a cation

• A negatively charged ion is an anion.Mg

O

+2

-2

positively t

negatively n n

Compounds are two or more elements that are held together by opposite charge attraction.

Oxygen-8Magnesium-12 8 (+)10 (-)-2 Charge

12 (+)10 (-)+2 Charge

Metal Non-metal

Ionic Formulas• Ions combine in small, whole number

proportions so that the sum of oxidation numbers will be zero!

• Electrons are transferred from the metal to the non-metal– The metal become a cation (+ charge)

• Why?

– The non-metal becomes an anion (- charge)• Why?

Metals combine with non-metals

Metals loose electrons to non-metals

They attract because their charges are opposite.

Ionic Formulas

• These are called Binary Compounds– The prefix “bi” meaning two– Two elements bonding to form a compound

• The metal ion ALWAYS goes first, followed by the non-metal ion

So what does this look like?

Mg O+2 -2

Magnesium Oxide

So what does this look like?

Al S+3 -2

2 3

Aluminum Sulfide

So what does this look like?

Na Cl+1 -1

Sodium ChlorideA.k.a. Table Salt

Your Turn!

Na F+1 -1

Ba

Al

K Li

Br

SO

Cl

-2 -2

-1

-1

+3

+2

+1+1

Your Turn!

Na F Ba

Al

K Li

Br

SO

Cl

2 2

3

2

Now let’s Kick it up a notch!

Polyatomic Ions

• A group of 2 or more atoms that act as a single unit

• When a metal and a polyatomic ion bond this forms a tertiary compound– 3 or more elements reacting to form a

compound

POLYATOMIC IONS Polyatomic ions are mostly made of two non-metals.

Ions with -1 chargeperbromate BrO4

-

1

bromate BrO3-1

bromite BrO2-1

hypobromite BrO-1

perchlorate ClO4-1

chlorate ClO3-1

chlorite ClO2-1

hypochlorite ClO-

1

periodate IO4-1

iodate IO3-1

iodite IO2-1

hypoiodite IO-1

nitrate NO3-1

nitrite NO2-1

hydroxide OH-1

cyanide CN-1

acetateC2H3O2

-1

PermanganateMnO4

-1

bicarbonate HCO3-

1

Ions with a -2 Charge

carbonate CO3-2

sulfate SO4-2

sulfite SO3-2

chromate CrO4-2

dichromate Cr2O7-

2

oxalate C2O4-2

Ions with a -3 Charge

phosphate PO4-3

phosphite PO3-3

arsenate AsO4-3

Ions with +1 chargeammonium ion

NH4+1Yes, I can read your minds…

No you do not have to memorize these polyatomic ions.

You will receive a chart with these

Obviously!!!

Tertiary Compounds

• Polyatomics ions react as one unit, so you treat them the same when writing formulas– Use the criss-cross method

PONa-3

4

+1

3

Sodium Phosphate

Tertiary Compounds

SOMg-2

4

+2

Magnesium Sulfate

( )

Tertiary Compounds

NOAl-2

2

+3

2

Aluminum Nitrite

( )3

Yeah, I’ve got nothing.

Your Turn!

Na SO+1 -2

Ba

Al

K Li

PO

SONO

ClO

-1 -2

-3

-1

+3

+2

+1+1

2

4

4

2

3

Your Turn!

Na SO2 Ba

Al

K Li

PO

SONO

ClO

2

2

2

4

4

2

3

( )

( )

How do we know the charge of the elements?

Glad you asked!

N

Oxidation Numbers (most common)

La Hf Ta Re OsCe Ba Tl Pb Bi Po At RnIr Pt Au Hg

Y Zr Nb Mo Tc RuRb Sr In Sn Sb Te I XeRh Pd Ag Cd

Sc Ti V Cr Mn FeK Ca Ga Ge As Se Br KrCo Ni Cu Zn

Al Si P S Cl ArNa Mg

B C O F NeLi Be

H H He

Ac Rf Db Sg Rh HsFr Ra Mt

+1+2+31A

2A

8A

0-4-3-2-17A

6A5A4A3A

W

Nd Pm Sm Eu Gd TbCe Pr Yb LuDy Ho Er Tm

Np Am Cm BkTh Pa No LrCf Es Fm MdU Pu

Click on element to see its oxidation number(s)

+1 +2 +2 +3 +2 +4

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