Chemistry IANB Page 11

ChemistryIANB Page 11

READ: Chemical BondsDO: Ion notation review

Ionic BondsChemical Formulas of Binary CompoundsIonic Compounds

Chemical Bonds and Compounds

Two types of bonds in compounds.

IONIC

COVALENT

Determine the Type of Chemical Bond One method is to look at the type of element that is

reacting.

H2.1

He…

Li1.0

Be1.5

B2.0

C2.5

N3.0

O3.5

F4.0

Ne…

Na1.0

Mg1.2

Al1.5

Si1.7

P2.1

S2.4

Cl2.8

Ar…

K0.9

Ca1.0

Sc1.2

Ti1.3

V1.4

Cr1.6

Mn1.6

Fe1.6

Co1.7

Ni1.8

Cu1.8

Zn1.7

Ga1.8

Ge2.0

As2.2

Se2.5

Br2.7

Kr…

Rb0.9

Sr1.0

Y1.1

Zr1.2

Nb1.2

Mo1.3

Tc1.4

Ru1.4

Rh1.4

Pd1.4

Ag1.4

Cd1.5

In1.5

Sn1.7

Sb1.8

Te2.0

I2.2

Xe…

Cs0.9

Ba1.0

La1.1

Hf1.2

Ta1.3

W1.4

Re1.5

Os1.5

Ir1.6

Pt1.4

Au1.4

Hg1.4

Tl1.4

Pb1.6

Bi1.7

Po1.8

At2.1

Rn…

1

2 3 4 5 6 7

8Table of the Elements

When Metals react with Nonmetals, Ionic Bonds tend to form

Metals

Nonmetals

Metals and Nonmetals have different pulls on their electrons. The stronger nonmetals will take electrons from the

weaker metals forming Ionic Bonds

When nonmetals bond with each other, Covalent Bonds tend to form.

Nonmetals tend to have a similar pull on their electrons, so they will share electrons and form covalent bonds.

Determine the Type of Chemical Bond A second method is to look at the positions on the

Periodic Table of elements that are reacting.

H2.1

He…

Li1.0

Be1.5

B2.0

C2.5

N3.0

O3.5

F4.0

Ne…

Na1.0

Mg1.2

Al1.5

Si1.7

P2.1

S2.4

Cl2.8

Ar…

K0.9

Ca1.0

Sc1.2

Ti1.3

V1.4

Cr1.6

Mn1.6

Fe1.6

Co1.7

Ni1.8

Cu1.8

Zn1.7

Ga1.8

Ge2.0

As2.2

Se2.5

Br2.7

Kr…

Rb0.9

Sr1.0

Y1.1

Zr1.2

Nb1.2

Mo1.3

Tc1.4

Ru1.4

Rh1.4

Pd1.4

Ag1.4

Cd1.5

In1.5

Sn1.7

Sb1.8

Te2.0

I2.2

Xe…

Cs0.9

Ba1.0

La1.1

Hf1.2

Ta1.3

W1.4

Re1.5

Os1.5

Ir1.6

Pt1.4

Au1.4

Hg1.4

Tl1.4

Pb1.6

Bi1.7

Po1.8

At2.1

Rn…

1

2 3 4 5 6 7

8Electronegativities of the Elements

Atoms that are far apart on the Periodic Table have a bigger

difference tend to form Ionic Bonds

Atoms that are close together on the Periodic Table tend to form Covalent

Bonds

Chemical Bonds – Ionic Bond

Ionic Bonds

Sodium Chloride is an Ionically bonded substance.

It is formed from a Sodium atom and a Chlorine atom.

Sodium

Na Cl

Chlorine

Sodium has 1 electron in its outer energy level.

Chlorine has 7 electrons in itsouter energy level.

Sodium wants to give up its outer electron.

Chlorine wants to getanother electron.

Notice: The electron was completely

Exchanged from the sodium to the chlorine.

Sodium is now a positively charged ion: Na+1

Chlorine is now a negatively charged ion: Cl -1

+1 -1

Opposite charges attract.The positive Sodium Ion is pulled toward the negative Chlorine Ion.

Na+1 Cl-1

The attraction that holds the positive ion to the negative ion

is called an Ionic Bond.

We have created a a new substance the ionic compound:

Sodium Chloride.

Sodium ChlorideNaCl

The ionic compound that is the result of the transfer of eletrons is held together with an Ionic Bond.

Sodium is a highly reactive metal. If you were to put it in water it

would explode.

Chlorine is a highly reactive nonmetal.

It is extremely poisonous, even deadly, if it is inhaled.

But with the exchange of a single electron, we have created the ionic compound that is ordinary table

salt.

This shows the importance of chemical reactions

and chemical bonds.

Ionic Bonds with Lewis Models

Electron transfer Ions formed

Formation of Ionic BondsElectron is transferred from metal (group 1) to nonmetal (group 17)creating a Cation (1+) and an Anion (1-)

Ionic substances or Salts Usually solids with very high melting points. Usually dissolve in water.

Bohr Model

Lewis Model

Formation of Ionic BondsGroup 1 metal and Group 17 nonmetal

The transfer of one electron produces ions. The opposite electric charge of the ions

creates an attraction that is the ionic bond. Ionic bonding occurs between metals and

non-metals

Transfer of e- Ions result

Formation of Ionic BondsGroup 2 metal and Group 17 nonmetal – Mg2+ Cation and 2 Cl1- Anions

The transfer of two electrons from Mg to two Cl produces three ions in the ratio MgCl2

Ionic compounds of a metal and nonmetal are called salts

Formation of Ionic Bonds Group 2 metal and Group 17 nonmetal – Mg2+ Cation and 2 Cl1- Anions

Formation of CaBr2

Ca Br•••

•••••+

•

Br••

•••••

Ca2+ +Br

••

••••••

1-

Br••

••••••

1-

IANB Page 11Complete Ionic bonds – bonds of attraction

Chemical Formulas

The type of element is expressed by the chemical symbol of the element.

You know that the compound NaCl is composed of Sodium and Chlorine because the chemical formula includes both of their symbols.

A Chemical Formula tells which elements make up a compound and how many atoms of each element are needed to make a single molecule.

1 of 8

Home

NaClSymbol for

SodiumSymbol for Chlorine

Chemical Formulas 2 of 8

The more metallic element is written first in a chemical formula.

NaClSodiumMetal

ChlorineNonmetal

MgOMagnesium

MetalOxygen

Nonmetal

COCarbon

NonmetalOxygen

Nonmetal

Although Carbon is a nonmetal, it is to the left of Oxygen on the Periodic Table

which makes it more metallic than Oxygen.


The subscript tells you the number of atoms that are bonded together to make one molecule.

MgCl2

Subscript

The subscript 2 tells us that there are two Chlorine ions involved in bonds to make a

molecule of Magnesium Chloride.

There is no subscript on the Magnesium ion. This is because there is only one

Magnesium ion in this molecule. Subscripts of 1 are not written out.

This formula tells us that one molecule of Magnesium Chloride is composed of1 Magnesium bonded to 2 Chlorines.

Chemical Formulas

What do the following chemical formulas tell you?

4 of 8

NaCl

Li2S

Fe2O3

= 1 Sodium bonded to 1 Chlorine

= 2 Lithiums bonded to 1 Sulfur

= 2 Irons bonded to 3 Oxygens


Subscripts are extremely important in a chemical formula because they determine the compound.

CO2

CO2 is the formula for Carbon Dioxide.A molecule with 1 Carbon bonded to 2 Oxygens.

Carbon Dioxide is the gas you exhale all day long.

COCO is the formula for Carbon Monoxide.

A molecule with 1 Carbon bonded to 1 Oxygen.Carbon Monoxide is a deadly gas in your car’s

exhaust.

When you change the subscript, you change the number of atoms involved in bonds to make the

molecule and therefore you change the compound.CO2 and CO are two different compounds.

IANB page 12

Determine Formulas for Simple Salts Remember, atoms can’t take electrons unless they

can find someone to give. Atoms can’t give electrons unless they can find someone to take.

Na

Sodium, from Group 1, has 1 electron in its outer energy level.

Chlorine, from Group 7, has 7 electrons in its outer energy level.

Cl

Sodium wants to give one electron.

Chlorine wants to take one electron.

Since sodium wants to give one electron and chlorine wants to take one electron, a

molecule of Sodium Chloride is made up of one sodium bonded to one chlorine.

Na Cl

We can get the same information by looking at the charges the atoms take on after they react. These charges are sometimes called the valence or the oxidation number and

they result from a gain or loss of electrons.

Sodium in Group 1 takes on a +1 charge.

Chlorine in Group 7 takes on a –1 charge.

+1 -1

A molecule, by definition, must have an overall charge of Zero.

This means all the positive charges must equal all the negative charges.

(electrons lost = electrons gained)

One sodium atom with a +1 charge balances out one chlorine atom with a –1 charge.

So, a molecule of sodium chloride has one sodium atom bonded to one chlorine atom

and an overall charge of zero.

Determine Formulas for Simple Salts Write the chemical formula for Lithium Sulfide.

The name of the molecule is Lithium Sulfide.

So we know there must be at least one Lithium atom and

at least one Sulfur atom.

Li S

Lithium in Group 1 takes on a +1 charge.(Lithium wants to give 1e-)

Sulfur in Group 6 takes on a –2 charge.(Sulfur wants to get 2 e-)

Will one lithium react with one sulfur?

+1 -2

One Sulfur has a -2 charge but one Lithium has only a +1 charge. So…

To make a molecule with an overall charge of zero we need another positive charge.

That means we need another lithium atom.

The formula for Lithium Sulfide is Li2S.It takes two Lithiums to balance out

one Sulfur for an overall charge of zero.Notice: the charges on the atoms are not

included in the chemical formula.

Li2S

Li+1

Determine Formulas for Simple Salts Write the chemical formula for Calcium Chloride.

The name of the molecule is Calcium Chloride.

So we know there must be at least one Calcium atom and

at least one Chlorine atom.

Ca Cl

Calcium in Group 2 takes on a +2 charge.(Calcium wants to give 2e-)

Chlorine in Group 7 takes on a –1 charge.(Chlorine want to get 1 e-)

Will one Calcium react with one Chlorine?

+2 -1

One Calcium has a +2 charge but one Chlorine has only a -1 charge. So…

To make a molecule with an overall charge of zero we need another negative charge.

That means we need another chlorine atom.

The formula for Calcium Chloride is CaCl2.It takes two Chlorines to balance out

one Calcium for an overall charge of zero.Notice: the charges on the atoms are not


CaCl2

Cl-1

IONIC BONDING PRACTICEPage 10 IANB

Complete the table now by writing the formula of the compound formed by the ions given.

Remember the resulting Compound is neutral.

N-3 S-2 Cl-1

Li+1

Ca+2

Al+3

IONS

Li3NCa3N

2AlN

Li2SCaSAl2S3

LiClCaCl2AlCl3

Determine Formulas for Simple Salts – Ionic Bonds

IANB p 54

Write the chemical formulas for the following salts then click for the answers. IANB P10

Name Formula Name Formula

Sodium Bromide

Potassium Sulfide

Beryllium Oxide

Calcium Bromide

Lithium Oxide

Cesium Oxide

BariumFluoride

Strontium Chloride

NaBr

BeO

Li2O

BaF2

K2S

CaBr2

Cs2O

SrCl2

10 of 12Determine Formulas for Simple Salts – Ionic Bonds Determine the name of the following salt: NaCl

This molecule is composed of two different elements: Sodium & Chlorine.Write the name of the metal atom first.

Sodium Chlorine

Write the name of the nonmetal with the suffix - ide

Chloride

That’s it! Naming is easy for salts that are

composed of metals from Groups 1 & 2.That’s because these metals react the

same way every time.

Sodium always gives up one electron.Chlorine will accept one electron.

So, sodium and chlorine will only react with each other in a 1 to 1 ratio.

The name Sodium Chloride says it all.

11 of 12Determine Formulas for Simple Salts – Ionic Bonds Determine the name of the following salt: CaCl2

This molecule is composed of two different elements: Calcium & Chlorine.Write the name of the metal atom first.

Calcium Chlorine

Write the name of the nonmetal with the suffix - ide

Chloride

That’s it! Naming is easy for salts that are



Calcium always gives up two electrons.Chlorine will accept one electron.

So, calcium and chlorine will only react with each other in a 1 to 2 ratio.

The name Calcium Chloride says it all.

Determine Formulas for Simple Salts – Ionic Bonds

12 of 12

Write the name of the salt given the chemical formula then click for the answers. IANB P10

Formula Name Formula Name

NaF K2O

MgO BeI2

Li2S BaBr2

Sodium Fluoride

Magnesium Oxide

Lithium Sulfide

Potassium Oxide

Beryllium IodideBarium Bromide

Home

Determine Formulas for Simple Salts – Ionic Bonds Write the chemical formulas for the following salts

then click for the answers.


Sodium Bromide

Potassium Sulfide

Beryllium Oxide

Calcium Bromide

Lithium Oxide

Cesium Oxide

BariumFluoride

Strontium Chloride

NaBr

BeO

Li2O

BaF2

K2S

CaBr2

Cs2O

SrCl2

Group 1 metals lose 1e- and take on a +1 charge.Group 2 metals lose 2e- and take on a +2 charge.

But, what about all the other metals? What will they do when they react and form salts?

Other metals can give different numbers of electrons in different situations.

Iron can give 2e- or 3e- and take on a +2 or +3 charge.

Elements that can react differently in different situations are called multivalent.

Salts with Multivalent MetalsHome

Salts with Multivalent Metals 1 of 4

Determine the charge on the nickel in the compound NiBr3.

Ni Br3

Since Nickel is not in Group 1 or 2, we can’t be immediately sure of its charge.

But, we have some information that will help us figure it out.

First: NiBr3 is a molecule and by definition a molecule must have an

overall charge of zero

Overall Charge = Zero

Second: We don’t know how nickel reacted but we do know how

bromine reacted.

Nickel is a metal so it will give e-. That means bromine must take electrons.

Bromine is in Group 7 so it will probably take 1 electron.

Bromine takes 1 e-

With these two pieces of information we can begin to determine the charge

on nickel in this compound.

Step1: Write the charge on one of the atoms in which you have the most confidence (Bromine in this case).The charge on one Bromine = -1

- 1

Step2: Write the total charge on all of the bromines in this molecule.

There are 3 bromines in this molecule. One bromine is -1. So, three are –3.

- 3

Step 3: Balance out the total negative charges with positive charges.

We have 3 negative charges total. The charge on the whole atom is zero.

So, we must have 3 positive charges.

+ 3

Step 4: Distribute the positive charges to the remaining atoms.

We have 3 positive charges and only 1 nickel so all three positive charges

must have come from the one nickel.

+ 3

The nickel ion, in this particular compound NiBr3,

must have a positive 3 charge.

Charge on one Bromine

Charge on all 3 BrominesTotal positive

chargeto balance out -3

Charge on each remaining atom


Determine the charge on one copper in the compound Cu2O.

Cu2 O

Since copper is not in Group 1 or 2, we can’t be immediately sure of its charge.


First: Cu2O is a molecule and by definition a molecule must have an



Second: We don’t know how copper reacted but we do know how

oxygen reacted.

Copper is a metal so it will give e-. That means oxygen must take e-.

Oxygen is in Group 6 so it will take 2 electrons.

Oxygen takes 2 e-


on copper in this compound.

Step1: Write the charge on one of the atoms in which you have the most confidence (Oxygen in this case).The charge on one Oxygen = -2

- 2

Step2: Write the total charge on all of the oxygens in this molecule.

There is only one oxygen in this molecule. One oxygen is -2.

- 2




+ 2


We have 2 positive charges and two coppers so each copper must be +1

+ 1

Each copper, in this particular compound, Cu2O,,


Charge on one Oxygen

Charge on all the OxygensTotal positive




Determine the charge on the silver in the compound AgF.

Ag F

Since silver is not in Group 1 or 2, we can’t be immediately sure of its charge.


First: AgF is a molecule and by definition a molecule must have an



Second: We don’t know how silver reacted but we do know how

fluorine reacted.

Silver is a metal so it will give e-. That means fluorine must take e-.

Fluorine is in Group 7 so it will take 1 electron.

Fluorine takes 1 e-


on silver in this compound.

Step1: Write the charge on one of the atoms in which you have the most confidence (Fluorine in this case).The charge on one Fluorine = -1

- 1

Step2: Write the total charge on all of the fluorines in this molecule.

There is only one fluorine in this molecule. One fluorine is -1.

- 1


We have 1 negative charge total. The charge on the whole atom is zero.

So, we must have 1 positive charge.

+ 1


We have 1 positive charge and one silver so that silver must be +1

+ 1

Each silver, in this particular compound, AgF,,


Charge on one Fluorine

Charge on all the FluorinesTotal positive




Determine the charge on one iron in the compound Fe2S3.

Fe2 S3

Since Iron is not in Group 1 or 2, we can’t be immediately sure of its charge.


First: Fe2S3 is a molecule and by definition a molecule must have an



Second: We don’t know how iron reacted but we do know how

sulfur reacted.

Iron is a metal so it will give e-. That means sulfur must take electrons.

Sulfur is in Group 6 so it will probably take 2 electrons.

Sulfur takes 2 e-


on iron in this compound.

Step1: Write the charge on one of the atoms in which you have the most

confidence (Sulfur in this case).The charge on one Sulfur = -2

- 2

Step2: Write the total charge on all of the sulfurs in this molecule.

There are 3 sulfurs in this molecule. One sulfur is -2. So, three are –6.

- 6




+ 6


We have 6 positive charges and two irons so each iron must be +3

+ 3

Each iron, in this particular compound Fe2S3,


Charge on one Sulfur

Charge on all 3 SulfursTotal positive




Determine the charge on one of the metal atoms in salts listed below.

Formula Charge Formula Charge

Li2O Co2O3

SnO MnCl3

Cu2S HgCl

PbO2 CrO3

Li = +1

Sn = +2

Cu = +1

Pb = +4

Co = +3

Mn = +3

Hg = +1

Cr = +6

Salts with Multivalent Metals10 of 13

Let’s name two salts that are composed of a multivalent metal.

Fe2 O3 Fe O

Both of these salts are composed of Iron (Fe) and Oxygen (O).

Iron Oxide Iron Oxide

We can’t call both compounds Iron Oxide because they are two different compounds

with different formulas.

To properly name these two compounds, we have to know the form of the metal.

In other words, we have to find the charge on one metal atom in each compound.

Remember: The overall charge on a molecule is zero.

Start with the atom in which you have the most confidence. Oxygen in Group 6 is -2

Step 1: Write the charge on one Oxygen.

Oxygen from Group 6 wants 2 electrons so it will take on a –2 charge.

- 2 - 2

Step 2: Write the total charge on all the Oxygens.

1st Molecule 3 Oxygens each is –22nd Molecule 1 Oxygen which is -2

- 6 - 2

Step 3: Balance out the total negative charges with

an equal number of positive charges. The overall charge on a molecule is zero

+ 6 + 2

Step 4: Divide the total positive charge

among the metal atoms.1st Molecule 2 Fe 2nd Molecule 1Fe

+ 3 + 2

The rest of the names for these two molecules is determined

by the charge on the metal.

Each iron atom in the first molecule has a +3 Charge.

This molecule is called Iron III Oxide(say: iron three oxide)

III

Each iron atom in the second molecule has a +2 Charge.

This molecule is called Iron II Oxide(say: iron two oxide)

II

Name Salts with Multivalent Metals

11 of 13

Let’s name two salts that are composed of a multivalent metal.

Cu2 S Cu Cl2

Both of these salts are composed of Copper (Cu).

One combines with Sulfur (S). The other combines with Chlorine (Cl).

Copper Sulfide Copper Chloride

We can’t just call these compounds Copper Sulfide and Copper Chloride because we don’t know which form of

copper is in which molecule.

To properly name these two compounds, we have to know the form of the metal.

In other words, we have to find the charge on a copper atom in each compound.


Start with the atom in which you have the most confidence. Sulfur = -2 Chlorine = -1

Step 1: Write the charge on 1 Sulfur & 1 Chlorine.Sulfur (Group 6) wants 2 e- –2 charge.

Chlorine (Group 7) wants 1 e- -1 charge.

- 2 - 1

Step 2: Write the total charge on all the nonmetals.

1st Molecule 1 Sulfur which is –22nd Molecule 2 Chlorines each is -1

- 2 - 2



+ 2 + 2


among the metal atoms.1st Molecule 2 Cu 2nd Molecule 1Cu

+ 1 + 2

The rest of the names for these two molecules is determined


Each Copper atom in the first molecule has a +1 Charge.

This molecule is called Copper I Sulfide(say: copper one sulfide)

I

Each copper atom in the second molecule has a +2 Charge.

This molecule is called Copper II Chloride(say: copper two chloride)

II

Salts with Multivalent Metals12 of 13

Write the name of the salt given the chemical formula then click for the answers. (Remember to check charge on the metal).Formula Name Formula Name

SnF2 NiBr3

Au2O Au2S3

PbS2 CrO3

HgCl2 Mn2O7

Tin II FluorideGold IOxide

Lead IV Sulfide

Nickel IIIBromideGold IIISulfide

Chromium VIOxide

Mercury IIChloride

Manganese VIIOxide

Salts with Polyatomic Ions 2 of 14

Let’s look at the term Polyatomic Ion.

A Polyatomic Ion is two or more atoms that are covalently bonded together that have a charge.

The next slide contains some examples of polyatomic ions. It includes the formula, the charge, and the name.

“Poly-” means Many

“-Atomic” refers to atoms

“Ion” means Has a Charge


Common Polyatomic Ions

Name Formula Charge

Ammonium NH4+ +1

Nitrite NO2- -1

Nitrate NO3- -1

Sulfate SO4-2 -2

Phosphate PO4-3 -3

Carbonate CO3-2 -2

Bicarbonate HCO3- -1

Acetate C2H3O2- -1

Salts withPolyatomic Ions 4 of 14

Polyatomic Ions can bond with other atoms to form molecules.

Notice, most of the polyatomic ions have negative charges and are composed of nonmetals.

These negative polyatomic ions often form bonds with positive metal ions creating molecules that we will classify as salts.

These salts are generally held together with ionic bonds while the polyatomic ions themselves are held together with covalent bonds.


Write the formula for Calcium Sulfate.

The name of the molecule is Calcium Sulfate.

So we know there must be at least one Calcium atom.

Ca

We know what Calcium means in Calcium Sulfate, but what does Sulfate stand for?Sulfate is the name of a polyatomic ion.

SO4-2

SO4

Calcium in Group 2 takes on a +2 charge.

The Sulfate ion always has a –2 charge.

+2 -2

One calcium with a +2 charge balances out one sulfate ion with a –2 charge.

So, a molecule of Calcium Sulfate has one Calcium ion bonded

to one Sulfate ion

The formula for Calcium Sulfate is CaSO4.One Calcium balances out one Sulfate

for an overall charge of zero.Notice: the charges on the ions are not


CaSO4

How did we know that the formula for Calcium Sulfate was CaSO4 and not CaS.

CaS is Calcium Sulfide. Polyatomic ions generally have names that

end with something other than –ide.

You can usually recognize the name of a polyatomic ion because it ends with

-ate, -ite, -ium.One exception is the Hydroxide Ion OH-1.

We will discuss this ion later.


Write the formula for Lithium Carbonate.

The name of the molecule is Lithium Carbonate.

So we know there must be at least one Lithium atom and

at least one Carbonate ion (CO3-2).

Li CO3

Lithium in Group 1 takes on a +1 charge.(Lithium wants to give 1e-)

Carbonate is the name of a polyatomic ion(CO3) that always has a –2 charge.

Will one lithium react with one Carbonate?

+1 -2

One Carbonate ion has a -2 charge but one Lithium has only a +1 charge. So…

To make a molecule with an overall charge of zero we need another positive charge.

That means we need another lithium.

Lithium Carbonate has the formula Li2CO3.It takes two Lithiums to balance out

one Carbonate for an overall charge of zero.Note: Carbonate refers to the CO3

-2 ion Carbonide would refer to plain Carbon (C)

Li2CO3

Li+1


Write the chemical formula for Copper II Nitrate.

The name of the molecule is Copper II Nitrate.

So we know there must be at least one Copper atom and

at least one Nitrate ion (NO3-1) .

Cu NO3

The fact that it is Copper II tells us that we are dealing with Copper with a +2 charge.

Nitrate (NO3) is a polyatomic ion that always has a –1 charge.

Will one Copper react with one Nitrate?

+2 -1

One Copper has a +2 charge but one Nitrate has only a -1 charge. So…

To make a molecule with an overall charge of zero we need another negative charge.That means we need another Nitrate Ion.

Copper II Nitrate is Cu(NO3)2.It takes two nitrate ions to balance out

one Copper for an overall charge of zero.Notice: The nitrate ion is put in parentheses

with the subscript behind. Why?

Cu NO3

NO3

-1

( )2

It is written this way to show that we are involving two nitrate groups.

The parentheses show that the subscript goes with the entire polyatomic ion not just

with the atom directly in front of it.


Write the chemical formula for Iron II Phosphate.

The name of the molecule is Iron II Phosphate.

So we know there must be at least one Iron atom and

at least one Phosphate ion (PO4-3) .

Fe PO4

The fact that it is Iron II tells us that we are dealing with Iron with a +2 charge.

Phosphate (PO4) is a polyatomic ion that always has a –3 charge.

Will one Iron react with one Phosphate?

+2 -3

One Iron has a +2 charge but one Phosphate has a -3 charge. So…

To make a molecule with an overall charge of zero, we need more ions of each type.

Fe PO4

PO4

-3

( )2

In cases like these, look at the ion with the larger charge (PO4

-3). One phosphate has a –3 charge.

You can’t balance that out with Fe+2 ions. One isn’t enough two is too many. So…

Since it won’t balance using only one Phosphate ion (PO4

-3), try two phosphates. Two phosphate ions (PO4

-3) will give you a total of 6 negative charges.

Can you balance out a –6 with Fe+2 ions?

-6

You can you balance six negative charges with three with Fe+2 ions which equals +6.

This makes the charge on the whole molecule equal to zero.

Fe+2

Fe+2

+6

Iron II Phosphate is Fe3(PO4)2.It takes three Irons to balance two

Phosphate ions for an overall charge of zero.Notice: The phosphate ion is put in

parentheses but the iron isn’t. Why?

3

It is written this way to show that we are involving two phosphate groups and three iron ions.

The parentheses show that the subscript goes with the entire polyatomic ion

not just with the atom directly in front of it.


Write the chemical formulas for the following compounds then click for the answers.


Lithium Bicarbonate

Chromium VI Nitrate

Potassium Sulfate

Cobalt II Phosphate

Beryllium Nitrite

Nickel III Carbonate

Calcium Acetate

Tin IV Phosphate

LiHCO3

K2SO4

Be(NO2)2

Ca(C2H3O2)2

Cr(NO3)6

Co3(PO4)2

Ni2(CO3)3

Sn3(PO4)4

Ion Formula

Ammonium NH4 +1

Nitrite NO2 -1

Nitrate NO3 -1

Sulfate SO4 -2

Phosphate PO4 -3

Carbonate CO3 -2

Bicarbonate HCO3 -1

Acetate C2H3O2 -1

Salts with Polyatomic Ions10 of 14

You have been writing chemical formulas for salts composed of polyatomic ions.

Next you will write the names of these salts when given the chemical formula.

The good news is that most of the rules you learned to this point still apply. Name the most metallic element first If the metal is mulitvalent, its charge will be in the

name.

The difference is that the nonmetal+ide ending is replaced by the name of the polyatomic ion.

11 of 14

Salts with Polyatomic Ions

Name of the following salt: Mg(NO3)2

This molecule is composed of Magnesium & Nitrate ions.

Write the name of the metal atom first.

Magnesium Nitrate

Write the name of the Polyatomic Ion

That’s it! Naming is simple for salts that are



Magnesium always gives up 2 electrons.It always has a –2 charge.

The Nitrate ion always has a –1 charge.Since the charges are always the same, there

is no reason to include them in the name


Name the following salt: Cu3(PO4)2

Cu3 (PO4)2

This salt is composed ofCopper (Cu) and Phosphate ions (PO4

-3).

Copper Phosphate

We can’t just call this compound Copper Phosphate because Copper is one

of those unpredictable metals.

To properly name this compound, we have to know the form of the metal.

In other words, we have to find the charge on one copper atom in this compound.


Start with the atom in which you have the most confidence. PO4 has a –3 charge

Step 1: Write the charge on one Phosphate.

The Phosphate ion always has a negative three charge

- 3

Step 2: Write the total charge on all the Phosphates

There are two phosphates each has a –3 charge which gives a total of -6

- 6



+ 6


among the metal atoms.There are three copper ions.

+ 2

The rest of the name for this molecule is determined


Each Copper atom has a +2 Charge.This molecule is Copper II Phosphate

(say: copper two phosphate)

II


Write the name of the salt given the chemical formula then click for the answers. (Remember to check charge on the metal).

Formula Name Formula Name

Ba(NO2)2 NaC2H3O2

CuNO3 Au2(SO4)3

Sn3(PO4)4 Cr(CO3)3

Hg(HCO3)2 Mn2(SO4)7

Barium Nitrite

Copper INitrate

Tin IV Phosphate

Sodium Acetate

Gold IIISulfate

Chromium VICarbonate

Mercury IIBicarbonate

Manganese VIISulfate

Ion Formula

Ammonium NH4 +1

Nitrite NO2 -1

Nitrate NO3 -1

Sulfate SO4 -2

Phosphate PO4 -3

Carbonate CO3 -2

Bicarbonate HCO3 -1

Acetate C2H3O2 -1

Chemistry

You have Completed Ionic Bonding& Chemical Formulas of Binary Salts

Adapted by Vern Ogle from John W. Pluemer

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Chemistry IANB Page 11