Chemical Names and Formulas Chapter 9 What's in a name? that which we call a rose By any other name would smell as sweet

Chemical Names and Formulas

Chapter 9

What's in a name? that which we call a roseBy any other name would smell as sweet

Introduction• Naming of ionic and molecular compounds

require memorization and knowledge of some basic rules.

• Deriving formulas from chemical names also require memorization and knowledge of some basic rules.

• Acids and bases are unique compounds that are named using simple rules.

• Two laws express how elements come together to form compounds.

Naming IonsSection 9.1

• Monatomic Ions

• Polyatomic Ions

Review: What is an ionic bond?• Ionic bonds: The

electrostatic forces that hold ions together in ionic compounds.

• One atom gives up electrons and the other picks up electrons.

Na+ Cl-

Na + Cl → Na+ + Cl-

(1s22s22p63s1) (1s22s22p63s23p5 ) (1s22s22p6) (1s22s22p63s23p6 )

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I.) Monatomic Ions

• These are ions that consists of a single atom with a positive or a negative charge.

• Naming these ions is fairly straight forward.

• Exception: The transition metals.

Cations of Representative Metals

• Group 1A,2A, and aluminum from 3A loses the same number of electrons as given by their group number.

Use the name of the metal followedby the word “ion” or “cation.”

Monatomic Anions

• Only nonmetals form anions.

• The charge of any anion of the representative elements is determined by subtracting 8 from the group number.

Start with the stem of the element name and add –ide to the end.

Transition Metals

• Many of these transition metals form more than one cation with different ionic charges.

• Two naming systems used to name these transition metals:– Stock system– An older system

The Stock System

• This is the preferred method for naming cations of transition metals.

• No space is left between the element name and the Roman numeral.

• All this is followed by the word “ion.”

A Roman numeral is place in parentheses and placed after the name of the element to indicate the numerical value of the charge on the ion.

The Older System

• It makes use of the “classical” names of the elements.

• Uses two suffixes:– ous: Used with the cation with the lower

charge. (Ferrous = Fe2+)– ic: Used with the cations with the higher

charge (Ferric = Fe3+)

II.) Polyatomic Ions• These are ions that are composed of more

than one atom.

• The atoms of these ions are covalently bonded together.

• These ions are treated as one unit.

• Most are anions and we need to know only one cation. (NH4

+ = ammonium)

Naming Polyatomic Anions

• Most of these ions you will need to memorize. (See Table 9.3 p. 257)

• -ite: One less oxygen (SO32- = Sulfite)

• -ate: One more oxygen (SO42- = Sulfate)

The names of most polyatomic anions end with the suffix –ite or –ate.

Naming & Writing Formulas for Ionic Compounds

Section 9.2

• Binary Ionic Compounds

• Compounds with Polyatomic Ions

Sodium chlorideNaCl

Sodium BicarbonateNaHCO3

I. ) Binary Ionic Compounds

Binary compound: A compound composed of onlytwo elements and can be either ionic or molecular.

Sodium chlorideNaCl

Naming Binary Ionic Compounds

• First verify that the compound is binary.

• Place the name of the cation ion first followed by the anion.

• For transition metals include the Roman numerals.

Let’s work through some samples.

Name the following compound: CaS.

1. Is the compound binary?

2. Name of cation:

3. Is cation derived from a transition metal?

4. Name of anion:

5. Name of compound:

Name the following compound: SnF2.


2. Name of cation:


4. Name of anion:


Name the following compound: SnO2.


2. Name of cation:


4. Name of anion:


Writing Formulas for Binary Ionic Compounds• If you know the name of a binary ionic

compound you can write its formula.• First, write the symbols for the cations and

anions.• Second, use subscripts to balance out the

charges.• Use the “crisscross” method.• No charges should be seen in the final

answer.

Give the formula for the following compound: potassium chloride.1. Is this a binary compound?

2. What is the cation?

3. Symbol for cation:

4. What is the anion?

5. Symbol for anion:

6. Does one cation and one anion balance each other out?

7. If not, how many of each are needed to balance the charges?

Give the formula for the following compound: iron(III) oxide.1. Is this a binary compound?







Give the formula for the following compound: calcium sulfide.1. Is this a binary compound?







II.) Compounds with Polyatomic Ions• These ionic compounds have at least one

polyatomic ion.• Naming these compounds is similar to

naming binary compounds, if we treat the polyatomic ion as one unit.

Sodium BicarbonateNaHCO3

Naming Compound with Polyatomic Ions

• The key to naming these compounds is to

have the polyatomic ions memorized.

Write the name for the cation ion followed by the name of the anion,remembering that the anions will end in –ate or –ite.

Name the following compound: LiCN.


2. Name of cation:


4. Name of anion:


Name the followingcompo und: NaClO.


2. Name of cation:


4. Name of anion:


Name the following compound: NH4C2O4.1. Is the compound binary?

2. Name of cation:


4. Name of anion:


Writing Formulas for Polyatomic Ionic Compounds• The process for writing the formulas for

polyatomic ionic compounds is the same as for binary ionic compounds.

• First, write the symbols for the cation and anion.

• Second, balance the charges treating the polyatomic ions as one unit.

• Or simply use the crisscross method.

Give the formula for the following compound: potassium sulfate.1. Is this a binary compound?







Give the formula for the following compound: sodium nitrate.1. Is this a binary compound?







Give the formula for the following compound: calcium nitrate.1. Is this a binary compound?







Naming & Writing Formulas for molecular Compounds

Section 9.3• Naming

Binary Compounds

• Writing Formulas for Binary Molecular Compounds

Carbon dioxide

CO2

Carbon monoxideCO

Review: What is an covalent bond?

• Covalent bonds: The sharing of electrons between two atoms.

• One atom gives up electrons and the other picks up electrons.

I.) Naming Binary Molecular Compounds

• Use prefixes to distinguish between the different binary molecular compounds.

• Prefixes tell us how many of each atom is present in a molecule of a binary compound.

• Look at prefixes in Table 9.4 (p.269)• All binary molecular compounds end with

–ide.

Rules for Naming Binary Molecular Compounds

1. ID that the compound is molecular

2. Name the elements in the order listed in the formula

3. Use prefixes to indicate the number of each atom in the molecule.

• Omit mono- if the 1st element has only 1 atom• Drop the “o” from mono- if the 1st atom begins with a

vowel.

4. The name of the second element ends with –ide.

Name the following binary compound: CO2.

1. Is the compound molecular?

2. Name of 1st atom:

3. How many?

4. Prefix for 1st atom:

5. Name of 2nd atom:

6. How many?

7. Prefix for 2nd atom:


Name the following binary compound: N2O.



3. How many?



6. How many?



Name the following binary compound: Cl2O8.



3. How many?



6. How many?



II.) Writing Formulas of Binary Molecular Compounds

• Simply use the prefixes in the name to tell you the number of each atom of each element.

• Write the correct symbol for each element and include the number of atoms using a subscript.

Give the formula for the following compound: silicon dioxide.

1. Is this a molecular compound?

2. What is the 1st atom?

3. What is its prefix:

4. How many of the 1st atoms?

5. What is the 2nd atom?

6. What is its prefix?


8. What is the formula?

Give the formula for the following compound: Arsenic pentachloride.









Give the formula for the following compound: Iodine tribromide.









Naming & Writing Formulas for Acids & bases

Section 9.4• Naming

Acids• Writing

Formulas for Acids

• Names and Formulas for Bases

Sulfuric acid

H2SO4

Sodium hydroxide

NaOH

Acids

• This is a group of ionic compounds with special properties.

• Acids have many natural and synthetic uses.

• More on acids in chapter 19.

A compound that contains one or more hydrogen atom and produces hydrogen ions (H+) when dissolved in water.

I.) Naming Acids

• Treat acids as if they were anions combined with enough hydrogen ions to make a neutral compound.

• Acids will have the basic formula HnX, where “n” is the number of hydrogens and “X” is a monatomic or polyatomic ion.

• Three rules for dealing with the naming of acids.

Rule #1: Compounds That End in -ide

• These compounds are often binary molecular compounds that do not have oxygen as a component.

1. Acid name begins with prefix hydro-

2. Drop –ide and add –ic

3. Add the word “acid” at the end

Give the name of the following acid: HCl.

1. Is this a binary compound?

2. What is the prefix?


4. Name of anion:

5. How does the suffix of the anion change?

6. What is the complete name of the acid?

Give the name of the following acid: H2S.




4. Name of anion:



Rule #2: Compounds That End in –ite

• The anions of these compounds have oxygen as a component.

• All of these are polyatomic acids.

• Do not use the prefix “hydro-”.

1. Drop –ite and add –ous.

2. Add the word “acid” at the end.

Give the name of the following acid: H2SO3.




4. Name of anion:



Give the name of the following acid: H3PO3.




4. Name of anion:



Rule #3: Compounds That End in –ate

• Again these acids are derived from compounds that have polyatomic anions with oxygen as a component.

• Do not use the prefix “hydro-”.

1. Drop –ate and add –ic.

2. Add the word “acid” at the end.

Give the name of the following acid: H3PO4.




4. Name of anion:



Give the name of the following acid: H2SO4.




4. Name of anion:



II.) Writing Formulas from Acid Names

• Simply use the reverse process to obtain the formulas from the names of the acids.

• Make sure that you include enough hydrogen ions (H+) to balance the charges of the anions.

Give the formula for the following compound: hydrochloric acid.1. Is this a binary compound?

2. How do you know?






Give the formula for the following compound: nitric acid.1. Is this a binary compound?

2. How do you know?






Bases

• Like acids, these are a special group of ionic compounds with many natural and synthetic uses.

• More on these compounds in chapter 19.

An ionic compound that produces hydroxide ions (OH-) when dissolved in water.

III.) Names and Formulas for Bases

• Bases are named in the same way as other ionic compounds – the name of the cation followed by the name of the anion.

• The key to identifying bases is to look for the OH- ion.

Give the formula for the following compound: potassium hydroxide.1. Is this a binary compound?







Give the formula for the following compound: Iron(III) hydroxide.1. Is this a binary compound?







Name the following binary compound: NaOH.1. Is the compound binary?

2. Name of cation:


4. Name of anion:


Name the following binary compound: Fe(OH)3.1. Is the compound binary?

2. Name of cation:


4. Name of anion:


The laws governing formulas and namesSection 9.5

• The Laws of Definite and Multiple Proportions

• Practicing Skills: Naming Chemical Compounds

• Practicing Skills: Writing Chemical Formulas

I.) The Laws of Definite and Multiple Proportions

• Elements combine to form compounds in very predictable ways.

• Thus we can describe the way they form compounds with two laws:

1. The Law Definite Proportions

2. The Law of Multiple Proportions

Law of Definite Proportions

• The ratios of atoms in a compound correlates to the ratio of masses of each element in that compound.

• This law is very important in stoichiometry and chemical equations (chapter 12).

In samples of any compound, the masses of the elements are always in the same proportions.

Example of The Law of Definite Proportions

• Let’s examine this law using MgS.

• The ratio of atoms is 1:1

• The mass ratio will also be 1:1

• Let’s see this for a 100g. sample of MgS.

Law of Multiple Proportions

• This law relates the mass of one element in a compound to the mass of another element in the same compound.

• This law is also important for stoichiometry.

Whenever the same two elements form more than one compound, the different masses of one element that combine with the same mass of the other are in the ratio of small whole numbers.

Example of The Law of Multiple Proportions

• Let’s examine this law using H2O and H2O2.

• Let’s see what the ration of oxygen is for the two compounds.

Sample Problem

Carbon reacts with oxygen to form two compounds. Compound A contains

2.41 g. of carbon for each 3.22 g. of oxygen. Compound B contains 6.71 g. of carbon for each 17.9 g. of oxygen. What is the lowest whole number mass ratio of carbon that combines with a given mass of oxygen?

Practicing Skills: Naming Chemical Compounds

Use this chart to help you write chemical names.

Practicing Skills: Writing Chemical Formulas

Use this chart to help you write chemical formulas.

Chemical Names and Formulas

Chapter 9

What's in a name? that which we call a roseBy any other name would smell as sweet

The End

Naming acids

These are the binary acids

These are the oxygen containing acids, or oxo acids.

Acids are ionic compounds where hydrogen is the cation.

Naming basesWe name bases as we name all other ionic compounds.• Name the following acids or bases:1. HF

2. HNO2

3. H3PO4

4. NaOH

• Give the formula for the following acids or bases:1. Lithium hydroxide2. Carbonic acid3. Hydrobromic acid4. Barium hydroxide

Bases are ioniccompounds in which the anions are mostly hydroxide.

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Chemical Names and Formulas Chapter 9 What's in a name? that which we call a rose By any other name would smell as sweet