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In this tutorial you will… Analyze a Chemical Formula Determine Formulas for Simple Salts Name Salts with Multivalent Metals Examine Salts with Polyatomic Ions Examine Chemical Formulas for Acids Examine Chemical Formulas for Bases Name Nonmetal Compounds

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(1)

Technical Science

Introduction to Chemistry

(2)

Chemical Formulas

In this tutorial you will…

Analyze a Chemical Formula

Determine Formulas for Simple Salts

Name Salts with Multivalent Metals

Examine Salts with Polyatomic Ions

Examine Chemical Formulas for Acids

Examine Chemical Formulas for Bases

(3)

Analyze a

Chemical Formula

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

NaCl

Symbol for Sodium

(4)

Analyze a

Chemical Formula

2 of 8

The more metallic element is written first in a

chemical formula.

NaCl

Sodium Metal

Chlorine Nonmetal

MgO

Magnesium Metal

Oxygen Nonmetal

CO

Carbon Nonmetal

Oxygen Nonmetal

Although Carbon is a nonmetal,

(5)

Analyze a

Chemical Formula

3 of 8

The subscript tells you the number of atoms that are

bonded together to make one molecule.

MgCl

2

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

(6)

Analyze a

Chemical Formula

What do the following chemical formulas tell you?

4 of 8

NaCl

Li

2

S

Fe

2

O

3

= 1 Sodium bonded to 1 Chlorine

= 2 Lithiums bonded to 1 Sulfur

(7)

Analyze a

Chemical Formula

5 of 8

Subscripts are extremely important in a chemical

formula because they determine the compound.

CO

2

A molecule with 1 Carbon bonded to 2 Oxygens.CO2 is the formula for Carbon Dioxide. Carbon Dioxide is the gas you exhale all day long.

CO

A molecule with 1 Carbon bonded to 1 Oxygen.CO is the formula for Carbon Monoxide.

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.

(8)

Analyze a

Chemical Formula

6 of 8

There is another number that you may see written

in front of a chemical formula.

This number is called the Coefficient.

The Coefficient is used to tell how many molecules

of the compound are present.

3MgCl

2

Coefficient

This tells us there are three molecules of Magnesium Chloride (MgCl2).

Each molecule has

(9)

Analyze a

Chemical Formula

7 of 8

Coefficients only tell the number of molecules

of a compound.

CO

2

2CO

2

3CO

2

= 1 molecule of Carbon Dioxide

= 2 molecules of Carbon Dioxide

= 3 molecules of Carbon Dioxide

Changing the Coefficient doesn’t change the compound. All the formulas above are carbon dioxide.

(10)

Analyze a

Chemical Formula

8 of 8

Interpret the following chemical formulas.

CaCl

2

2N

2

3Al

2

S

3

=

1 molecule of Calcium Chloride (CaCl

2

)

The molecule has 1 Calcium bonded

to 2 Chlorines.

=

2 molecules of Nitrogen Gas (N

2

)

Each molecule has 2 Nitrogen atoms

bonded to each other.

=

3 molecules of Aluminum Sulfide (Al

2

S

3

)

Each molecule has 2 Aluminum atoms

bonded to 3 Sulfurs.

(11)

Determine Formulas

for Simple Salts

1 of 12

You know what the subscript in a chemical

formula means but how do you know what those

subscripts should be?

Home

Why is sodium chloride always NaCl (one sodium

bonded to one chlorine)? Why is water always

H

2

O (2 hydrogens bonded to one oxygen)?

Again, we need to go back to “what atoms want”.

Atoms gain or lose electrons to fill the S & P

orbitals of their outer level.

(12)

Determine Formulas

for Simple Salts

2 of 12

In order to determine chemical formulas, we need

to have some compounds with which to work.

We are going to concentrate on compounds that are

composed of metals bonded to nonmetals.

These compounds are classified as Salts.

When you think of salt, you probably think of

Sodium Chloride (table salt). But this is just one

member of very large group of compounds.

(13)

Determine Formulas

for Simple Salts

3 of 12

Let’s start with the atoms from the Groups that

tend to do the same thing every time.

1 H 1.0 2 He 4.0 3 Li 7.0 4 Be 9.0 5 B 11.0 6 C 12.0 7 N 14.0 8 O 16.0 9 F 19.0 10 Ne 20.0 11 Na 23.0 12 Mg 24.5 13 Al 27.0 14 Si 28.0 15 P 31.0 16 S 32.0 17 Cl 35.5 18 Ar 40.0 19 K 39.0 20 Ca 40.0 21 Sc 45.0 22 Ti 48.0 23 V 51.0 24 Cr 52.0 25 Mn 55.0 26 Fe 56.0 27 Co 59.0 28 Ni 58.5 29 Cu 63.5 30 Zn 65.5 31 Ga 69.5 32 Ge 72.5 33 As 75.0 34 Se 79.0 35 Br 80.0 36 Kr 84.0 Group 1

2 3 4 5 6 7

8

Group e- in outer

S&P orbitals Reaction Resulting Ions 1 2 6 7 8 +1

+2 -2 -1

1 Lose 1 e- +1

2 Lose 2 e- +2

6 Gain 2 e- -2

7 Gain 1 e- -1

8 No

Reaction

(14)

Determine Formulas

for Simple Salts

4 of 12

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

(15)

Determine Formulas

for Simple Salts

5 of 12

Write the chemical formula for Magnesium Oxide.

The name of the molecule is Magnesium Oxide.

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

at least one Oxygen atom.

Mg O

Magnesium in Group 2 takes on a +2 charge.

Oxygen in Group 6 takes on a –2 charge.

+2 -2

One magnesium with a +2 charge balances out one oxygen with a –2 charge.

So, a molecule of Magnesium Oxide has one magnesium atom bonded

to one oxygen atom

The formula for Magnesium Oxide is MgO. One Magnesium balances out one Oxygen

for an overall charge of zero.

Notice: the charges on the atoms are not included in the chemical formula.

(16)

Determine Formulas

for Simple Salts

6 of 12

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.

(17)

Determine Formulas

for Simple Salts

7 of 12

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 included in the chemical formula.

CaCl

2

(18)

Determine Formulas

for Simple Salts

8 of 12

Write the chemical formulas for the following salts

then click for the answers.

Name

Formula

Name

Formula

Sodium

Bromide

Potassium

Sulfide

Beryllium

Oxide

Calcium

Bromide

Lithium

Oxide

Cesium

Oxide

Barium

Fluoride

Strontium

Chloride

NaBr

BeO

Li

2

O

BaF

2

K

2

S

CaBr

2

Cs

2

O

(19)

9 of 12

You have written chemical formulas when given the

name of the compound .

Next you will name compounds given the chemical

formula

Once again, we will be concentrating on salts that

are composed of metal atoms from Groups 1 & 2

bonded to nonmetal atoms from Groups 6 & 7

Let’s start with a familiar salt: NaCl.

(20)

10 of 12

Determine Formulas

for Simple Salts

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

Chlor

ide

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

(21)

11 of 12

Determine Formulas

for Simple Salts

Determine the name of the following salt: CaCl

2

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

Chlor

ide

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.

Calcium always gives up two electrons. Chlorine will accept one electron. So, calcium and chlorine will only react

(22)

Determine Formulas

for Simple Salts

12 of 12

Write the name of the salt given the chemical

formula then click for the answers.

Formula

Name

Formula

Name

NaF

K

2

O

MgO

BeI

2

Li

2

S

BaBr

2

Sodium

Fluoride

Magnesium

Oxide

Lithium

Sulfide

Potassium

Oxide

Beryllium

Iodide

Barium

Bromide

(23)

1 of 13

So far we have concentrated on salts whose metals

came from Groups 1 & 2.

These salts were easy to name and it was fairly

easy to determine their chemical formulas.

This is because the metals from Groups 1 & 2 are

very predictable. They do the same thing every

time they react.

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?

Name Salts with

(24)

2 of 13

All metals give up electrons when they react. (This

is characteristic of metals.) However, the metals

outside Groups 1 & 2 aren’t nearly as predictable.

Name Salts with

Multivalent Metals

Some of these metals, like those in Groups 1 & 2,

will always give the same number of electrons.

Zinc always gives 2e- and takes on +2 charge

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.

(25)

Name Salts with

Multivalent Metals

3 of 13

When working with salts made up of metals outside

Groups 1 & 2, we have to make sure we know

which form of the atom we are dealing with.

In other words, we need to know the charge on the

atoms that make up the compound. (especially the

metals)

What would you do if you were asked to find the

charge on the Sodium ion in NaCl.

This is easy. Sodium is in Group 1. It’s always +1.

(26)

Name Salts with

Multivalent Metals

4 of 13

Determine the charge on the nickel in the

compound NiBr

3

.

Ni Br

3

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 NiBr

3,

must have a positive 3 charge.

Charge on one Bromine

Charge on all 3 Bromines Total positive charge

(27)

Name Salts with

Multivalent Metals

5 of 13

Determine the charge on one copper in the

compound Cu

2

O.

Cu

2

O

Since copper 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: Cu2O is a molecule and by definition a molecule must have an

overall charge of zero

Overall Charge = Zero

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-With these two pieces of information

we can begin to determine the charge 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

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

We have 2 negative charges total. The charge on the whole atom is zero.

So, we must have 2 positive charges.

+ 2

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

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

+ 1

Each copper, in this particular compound, Cu

2O,,

must have a positive 1 charge.

Charge on one Oxygen

Charge on all the Oxygens Total positive charge

(28)

Name Salts with

Multivalent Metals

6 of 13

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.

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

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

overall charge of zero

Overall Charge = Zero

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-With these two pieces of information

we can begin to determine the charge 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

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

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

So, we must have 1 positive charge.

+ 1

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

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

+ 1

Each silver, in this particular compound, AgF,

,

must have a positive 1 charge.

Charge on one Fluorine

Charge on all the Fluorines Total positive charge

(29)

Name Salts with

Multivalent Metals

7 of 13

Determine the charge on one iron in the compound

Fe

2

S

3

.

Fe

2

S

3

Since Iron 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: Fe2S3 is a molecule and by definition a molecule must have an

overall charge of zero

Overall Charge = Zero

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-With these two pieces of information

we can begin to determine the charge 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

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

We have 6 negative charges total. The charge on the whole atom is zero.

So, we must have 6 positive charges.

+ 6

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

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

+ 3

Each iron, in this particular compound Fe2S3,

must have a positive 3 charge.

Charge on one Sulfur

Charge on all 3 Sulfurs Total positive charge

(30)

Name Salts with

Multivalent Metals

8 of 13

Determine the charge on one of the metal atoms in

salts listed below.

Formula

Charge

Formula

Charge

Li

2

O

Co

2

O

3

SnO

MnCl

3

Cu

2

S

HgCl

PbO

2

CrO

3

Li = +1

Sn = +2

Cu = +1

Pb = +4

Co = +3

Mn = +3

Hg = +1

(31)

Name Salts with

Multivalent Metals

9 of 13

Dealing with these unpredictable metals is more

difficult than dealing with the Group 1 & 2 metals.

Naming salts composed of these metals is also a bit

more difficult.

A simple salt like NaCl is called Sodium Chloride.

Sodium will only give 1 electron. When chlorine

takes, it only takes one electron. Therefore, there is

only one way that sodium can react with chlorine.

Before we can name salts with unpredictable

(32)

Name Salts with

Multivalent Metals

10 of 13

Let’s name two salts that are composed of a

multivalent metal.

Fe

2

O

3

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 –2 2nd 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)

(33)

Name Salts with

Multivalent Metals

11 of 13

Let’s name two salts that are composed of a

multivalent metal.

Cu

2

S

Cu Cl

2

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.

Remember:

The overall charge on a molecule is zero. 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 –2

2nd Molecule 2 Chlorines each is -1

- 2

- 2

Step 3:

Balance out the total negative charges with an equal number of positive charges. The overall charge on a molecule is zero

+ 2

+ 2

Step 4:

Divide the total positive charge among the metal atoms.

1st Molecule 2 Cu 2nd Molecule 1Cu

+ 1

+ 2

The rest of the names for these two molecules is determined

by the charge on the metal.

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)

(34)

Name Salts with

Multivalent Metals

12 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

SnF

2

NiBr

3

Au

2

O

Au

2

S

3

PbS

2

CrO

3

HgCl

2

Mn

2

O

7

Tin II

Fluoride

Gold I

Oxide

Lead IV

Sulfide

Nickel III

Bromide

Gold III

Sulfide

Chromium VI Oxide

Mercury II

Chloride

(35)

Name Salts with

Multivalent Metals

13 of 13

Why don’t we call NaCl; Sodium I Chloride

Α

Sodium is in Group 1. The metals in Group 1

always react the same way. They will only give up

one electron. So…

Sodium will always take on a positive 1 charge

(Na

+1

). Since the charge on sodium is always +1,

there is no reason to include it in the name.

The same is true for Group 2 metals. They are

always +2. So, we can just write Calcium Oxide.

We don’t have to say Calcium II Oxide.

(36)

Examine Salts with

Polyatomic Ions

1 of 14

To this point, when we talked about forming

chemical bonds, we always said these bonds link

two or more atoms together to form a molecule.

A molecule has an overall charge of zero.

However, it is possible for atoms to form bonds but

still have a positive or negative overall charge.

These groups of bonded atoms can’t be called

molecules because they don’t balance out to zero.

The groups of bonded atoms are Polyatomic Ions.

(37)

Examine 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

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

(38)

Examine Salts with

Polyatomic Ions

3 of 14

Common Polyatomic Ions

Name

Formula

Charge

Ammonium

NH

4+

+1

Nitrite

NO

2-

-1

Nitrate

NO

3-

-1

Sulfate

SO

4-2

-2

Phosphate

PO

4-3

-3

Carbonate

CO

3-2

-2

Bicarbonate

HCO

3-

-1

(39)

Examine Salts with

Polyatomic 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.

(40)

Examine Salts with

Polyatomic Ions

5 of 14

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. SO

4 -2

SO

4

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 included in the chemical formula.

CaSO

4

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.

(41)

Examine Salts with

Polyatomic Ions

6 of 14

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 CO

3

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)

(42)

Examine Salts with

Polyatomic Ions

7 of 14

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 NO

3

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 NO

3

NO

3

-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

(43)

Examine Salts with

Polyatomic Ions

8 of 14

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 PO

4

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 PO

4

PO

4

-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 Fe

3(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

(44)

Examine Salts with

Polyatomic Ions

9 of 14

Write the chemical formulas for the following

compounds then click for the answers.

Name Formula Name Formula

Lithium Bicarbonate

Chromium VI Nitrate Potassium

Sulfate

Cobalt II Phosphate Beryllium

Nitrite

Nickel III Carbonate Calcium

Acetate

Tin IV Phosphate

LiHCO

3

K2SO4

Be(NO

2)2

Ca(C

2H3O2)2

Cr(NO3)6

Co3(PO4)2

Ni2(CO3)3

Sn

3(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

(45)

Examine Salts with

Polyatomic Ions

10 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.

(46)

11 of 14

Examine Salts with

Polyatomic Ions

Name of the following salt: Mg(NO

3

)

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 composed of metals from Groups 1 & 2.

That’s because these metals react the same way every time.

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

(47)

Examine Salts with

Polyatomic Ions

12 of 14

Name the following salt: Cu

3

(PO

4

)

2

Cu

3

(PO

4

)

2

This salt is composed of

Copper (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.

Remember:

The overall charge on a molecule is zero. 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

Step 3:

Balance out the total negative charges with an equal number of positive charges. The overall charge on a molecule is zero

+ 6

Step 4:

Divide the total positive charge among the metal atoms.

There are three copper ions.

+ 2

The rest of the name for this molecule is determined by the charge on the metal.

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

(say: copper two phosphate)

(48)

Examine Salts with

Polyatomic Ions

13 of 14

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

Sn

3(PO4)4 Cr(CO3)3

Hg(HCO3)2 Mn2(SO4)7 Barium

Nitrite

Copper I Nitrate

Tin IV Phosphate

Sodium Acetate

Gold III Sulfate

Chromium VI Carbonate

Mercury II

Bicarbonate 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

(49)

Examine Salts with

Polyatomic Ions

14 of 14

So far in this tutorial we have explored the group of

compounds called salts.

We determined chemical formula from the name.

We determined the name from the formula.

We found the charges on the ions in a salt.

We made salts using polyatomic ions.

Remember: Salts are composed of a metal and a

nonmetal and they tend to be ionically bonded.

In the rest of the tutorial we will explore three other

groups, Acids, Bases, and Nonmetal compounds.

(50)

Home

Examine Chemical

Formulas for Acids

1 of 9

In this section we wills study a group of compounds

called acids.

Acids are compounds that dissolve in water to

release Hydrogen Ions (H

+1

).

Hydrogen has 1 proton & 1 electron. It must lose

that electron to form a hydrogen ion (H

+1

).

A hydrogen ion, then, is just a proton which is very

reactive.

(51)

Examine Chemical

Formulas for Acids

2 of 9

Let’s analyze the formula for a simple acid.

H Cl

You can recognize an acid when you see its formula because it starts with an H.

When an acid is dissolved in water it breaks up into ions.

It is the Hydrogen ions that give an acid its acidic properties.

H

+1

Cl

-1

The formula for this acid was determined in the same way that

we found the formulas for salts.

Hydrogen ions always have a +1 charge. Chlorine will get 1e- so it has a –1 charge.

One positive Hydrogen Ion balances one negative Chlorine Ion. So…

The acid molecule shown above is formed from

one hydrogen and one chlorine. Naming a simple acid is

slightly different from naming salts. The name of a simple acid has three parts.

The name of a simple acid starts with the prefix

Hydro-Hydro

Next you name the nonmetal (chlorine in this case)

with the suffix -ic

chloric

Last, you add the word Acid

at the end.

Acid

Hydrochloric Acid (HCl) is a common strong acid.

(52)

Examine Chemical

Formulas for Acids

3 of 9

Are the formulas for these simple acids correct?

H F

H Br

Acids are composed of Hydrogen Ions. Both of these compounds

start with an H.

Hydrogen Ions always have a +1 charge. Both Fluorine & Bromine are in Group 7.

They both want to get 1 electron so they both tend to take on a –1 charge.

H

+1

F

-1

H

+1

Br

-1

One positive Hydrogen Ion balances one negative Fluorine in the 1st molecule.

One positive Hydrogen Ion balances one negative Bromine in the 2nd molecule. One hydrogen ion with one fluorine ion is

the correct formula for the 1st molecule. One hydrogen ion with one bromine ion is

the correct formula for the 2nd molecule. The formulas for both

(53)

Examine Chemical

Formulas for Acids

4 of 9

How would you name these simple acids?

H F

H Br

Both of these compounds start with H

so we know they are acids. The name of a simple acid starts with the prefix

Hydro-Hydro

Hydro

Next, name the nonmetal (Fluorine and Bromine)

with the suffix -ic

fluoric

bromic

Last, add the word Acid

to the end.

Acid

Acid

Hydrofluoric Acid is a very strong acid. It is so reactive,

it can be used to etch glass.

Hydrobromic Acid is a very strong acid. It is used to generate other organic compounds and in the manufacture of

(54)

Examine Chemical

Formulas for Acids

5 of 9

Acids can also be formed from hydrogen ions

bonding to negative polyatomic ions.

We will call these acids complex as opposed to the

simple acids we just studied.

Just like simple acids, complex acids release

hydrogen ions when they are dissolved in water.

The more hydrogen ions an acid releases, the

(55)

Examine Chemical

Formulas for Acids

6 of 9

Determine the correct formulas for two complex

acids made from the Nitrate and Phosphate ions.

NO

3

PO

4

Acids release hydrogen ions so these formulas must include

Hydrogen.

H

H

Now we know the types of ions that will compose these two molecules but to determine their formulas, we need

to know the charge on the ions. Hydrogen = +1

Nitrate (NO

3) = -1

Phosphate (PO

4) = -3

+1 -1 +1 -3

Just like any other molecule, an acid must have an overall charge of zero.

Will one H+1 balance one NO

3 -1?

Will one H+1 balance one PO

4 -3?

One positive hydrogen ion balances one negative nitrate ion.

So the correct formula is HNO

3

HNO

3

It will take three hydrogen ions (each +1) to balance one Phosphate ion (-3)

so the correct formula is H

3PO4

H

+1

H

+1

(56)

Examine Chemical

Formulas for Acids

7 of 9

Determine the correct formula for complex acids

created from the polyatomic ions below.

Polyatomic Ion

Formula for the Acid

Sulfate

SO

4-2

Carbonate

CO

3-2

Acetate

C

2

H

3

O

2-1

(57)

Examine Chemical

Formulas for Acids

8 of 9

The table below shows the formula, names, and

uses for some common complex acids.

Formula

Name

Use

HNO

3

H

2

SO

4

H

3

PO

4

H

2

CO

3

HC

2

H

3

O

2

Nitric Acid

Strong Acid used to

make other chemicals

Sulfuric

Acid

Strong Acid Used as battery acid

Phosphoric

Acid

Weak Acid Used in Pickling

Carbonic

Acid

Weak Acid

In carbonated drinks

Acetic Acid

Weak Acid Vinegar

Notice:

The prefix Hydro- is dropped from

the names of complex acids

(58)

Examine Chemical

Formulas for Acids

9 of 9

What is it about an acid that gives it its acidic

properties?

Α

A compound is considered to be an acid if it

releases hydrogen ions H

+1

when dissolved in

water. The more hydrogen ions that are released

the stronger is the acid. Hydrogen ions are very

reactive particles which makes acids very reactive

compounds.

(59)

Home

1 of 6

Examine Chemical

Formulas for Bases

In this section we will study a group of compounds

called Bases.

The term base may be new but the terms alkaline or

caustic may be familiar. They all refer to bases.

Bases are compounds that dissolve in water to

release a particular polyatomic ion (OH

–1

)

The OH

-1

ion is called the Hydroxide Ion. Notice it

ends with –ide, this is an exception to our rule.

(60)

Examine Chemical

Formulas for Bases

2 of 6

Let’s analyze the formula for a Base.

Na OH

You can recognize a base when you see its formula because it ends with an OH. When a base is dissolved in water

it breaks up into ions.

It is the hydroxide ions (OH-1) that give a base its basic properties.

Na

+1

OH

-1

The formula for this base was determined in the same way that

we found the formulas for salts.

Hydroxide ions always have a -1 charge. Sodium will give 1e- so it has a +1 charge.

One positive Sodium Ion balances one negative Hydroxide Ion. So…

The base molecule shown above is formed from

one sodium and one hydroxide. Naming a base is the same

as naming salts composed of polyatomic ions.

Name the metal first.

Sodium

Next name the polyatomic ion. The polyatomic ion

associated with bases is the Hydroxide ion.

Hydroxide

Sodium Hydroxide (NaOH) is a common strong base.

(61)

Examine Chemical

Formulas for Bases

3 of 6

Determine the correct formula for the base

Calcium Hydroxide

Ca

OH

If the name is Calcium Hydroxide, then we must have

at least one Calcium and at least one Hydroxide ion. To determine the correct formula,

we have to know the charges

on the ions that make up the molecule. Ca (Group 2) = +2 OH = -1

+2

-1

Molecules have an overall charge of zero.

Will one calcium balance one hydroxide?

One Ca is +2 while one OH is –1. So, we will need two Hydroxide ions

to balance each Calcium.

OH

-1

The formula for Calcium Hydroxide

is Ca(OH)2

Ca(OH)

2

Remember the parentheses. They tell you that we need

(62)

Examine Chemical

Formulas for Bases

4 of 6

Name the base that was formed from the

multivalent metal shown in the compound below.

Fe (OH)

3

This base is formed from Iron and the Hydroxide ion.

Iron

Hydroxide

We can’t just call this base Iron Hydroxide because iron is multivalent.

We need to know the charge on this particular iron.

To find the charge on iron, start with the charge on the hydroxide ion.

Remember, the overall charge must be zero. Step 1

Write the charge on one hydroxide ion. Hydroxide is always has a –1 charge.

-1

Step 2

Write the total charge on all the hydroxide ions

Three hydroxides each has a –1 charge = -3.

-3

Step 3

Balance the three negative charges with three positive charges for an overall charge of zero.

+3

Step 4

Divide the positive charges among the remaining atoms. There is only one iron so

that iron must have a +3 charge.

+3

The name for Fe(OH)

3

is Iron III Hydroxide (say: iron three hydroxide)

(63)

Examine Chemical

Formulas for Bases

5 of 6

Fill in the missing pieces of the table below.

Name

Formula

LiOH

Potassium Hydroxide

Magnesium Hydroxide

Ni(OH)

2

Copper II Hydroxide

Aluminum Hydroxide

(Al is not multivalent.) (What charge will it take on?)

Lithium Hydroxide

KOH

Mg(OH)

2

Nickel II Hydroxide

Cu(OH)

2

Al(OH)

3

(64)

Examine Chemical

Formulas for Bases

6 of 6

What is it about a base that gives it its basic

properties?

Α

A compound is considered to be a base if it releases

hydroxide ions OH

-1

when dissolved in water. The

more hydroxide ions that are released the stronger

is the base. Hydroxide ions are very reactive

particles with makes bases very reactive

compounds. Bases are sometimes called alkaline

or caustic. They are used in cleaning compounds,

for fertilizer, and as antacids.

(65)

Name Nonmetal

Compounds

1 of 6

In this section, we will look at a few compounds

that are composed entirely of nonmetals.

We will learn the basics of naming nonmetal

compounds.

We won’t determine the chemical formulas for

nonmetal compounds from the charges.

This is because many nonmetals are multivalent.

Even those nonmetals in Groups 6 & 7 that we

counted on to be –2 and –1, can do many different

things when they react with other nonmetals.

(66)

Name Nonmetal

Compounds

2 of 6

1 H 1.0 2 He 4.0 3 Li 7.0 4 Be 9.0 5 B 11.0 6 C 12.0 7 N 14.0 8 O 16.0 9 F 19.0 10 Ne 20.0 11 Na 23.0 12 Mg 24.5 13 Al 27.0 14 Si 28.0 15 P 31.0 16 S 32.0 17 Cl 35.5 18 Ar 40.0 19 K 39.0 20 Ca 40.0 21 Sc 45.0 22 Ti 48.0 23 V 51.0 24 Cr 52.0 25 Mn 55.0 26 Fe 56.0 27 Co 59.0 28 Ni 58.5 29 Cu 63.5 30 Zn 65.5 31 Ga 69.5 32 Ge 72.5 33 As 75.0 34 Se 79.0 35 Br 80.0 36 Kr 84.0 37 Rb 85.5 38 Sr 87.5 39 Y 89.0 40 Zr 91.0 41 Nb 93.0 42 Mo 96.0 43 Tc 98.0 44 Ru 101.0 45 Rh 103.0 46 Pd 106.5 47 Ag 108.0 48 Cd 112.5 49 In 115.0 50 Sn 118.5 51 Sb 122.0 52 Te 127.5 53 I 127.0 54 Xe 131.0 55 Cs 133.0 56 Ba 137.5 57 La 139.0 72 Hf 178.5 73 Ta 181.0 74 W 184.0 75 Re 186.0 76 Os 190.0 77 Ir 192.0 78 Pt 195.0 79 Au 197.0 80 Hg 200.5 81 Tl 204.5 82 Pb 207.0 83 Bi 209.0 84 Po 209.0 85 At 210.0 86 Rn 222.0 Group 1

2 3 4 5 6 7

8

Noble Gases

Metals

Nonmetals

(67)

Name Nonmetal

Compounds

3 of 6

Name the two familiar nonmetal compounds below.

CO

CO

2

Naming nonmetal compounds is different from naming the salts, acids, and bases.

We will use Greek prefixes to show the number of each atom in the molecule.

Prefix Number

Mono - One Di - Two Tri - Three Tetra - Four Penta - Five Hexa - Six

Both of these compounds are composed of

Carbon and Oxygen.

Carbon

Oxygen

Carbon

Oxygen

The least metallic atom, Oxygen in this case,

gets the suffix –ide Oxygen becomes Oxide

ide

ide

Use the Greek prefixes, at the right, to show

how many atoms of each element are in the molecule.

In the first molecule (CO), there is one Oxygen =

Mono-In the second molecule (CO2), there are two Oxygens =

Di-Mono

Di

o

There is one Carbon in each molecule. When there is only one of the first atom

we don’t use the mono prefix.

It is understood that there is one carbon. The first molecule (CO) is called

Carbon Monoxide

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