Write formulas and names for ionic, polyatomic and covalent compounds using IUPAC nomenclature

Write formulas and names for ionic, polyatomic and covalent compounds using IUPAC nomenclature.

Write and classify balanced chemical equations from written descriptions of reactions.

Predict the products of chemical reactions, given the reactants and type of reaction.

Determine the average atomic mass using isotopes and their relative abundance.

Research the importance and application of isotopes.Describe the concept of the mole and its importance to

measurement in chemistry.Calculate the molar mass of various substances.Solve problems requiring conversions between moles, mass, and

number of particles.

UNIT 1Chemical Reactions

Part I

All atoms, except hydrogen, are made of 3 basic particles: protons, neutrons and electrons. Each element has a unique number of protons, which is indicated by its atomic number.

Anatomy of an Atom

The periodic table arranges atoms according to their properties. The periodic table below shows the names of several groups we will be referring to throughout this course.

met

als

non-

met

als

The outermost shell is called the valence shell. The electrons in the valence shell are called the valence electrons.

The atoms of elements in Period 1 have one shell. This shell contains a maximum of ____ electrons.

The atoms of elements in Period 2 have _____ shells. The valence shell contains a maximum of ______ electrons.

The atoms of elements in Period 3 have _____ shells. The valence shell contains a maximum of ______ electrons.

82

2

83

*Complete Electron Shell handout*

An ion is a charged particle. An ion is formed when a neutral atom gains or loses electrons. Positively charged ions are called cations, and negatively charged ions are called anions.

Ionic Compounds

*Complete “Keeping an ION That” handout*

Ionic compounds are formed when two or more oppositely charged ions are attracted to each other. This chemical attraction is called a chemical bond. An ionic bond is formed when a negatively charged ion is attracted to a positively charged ion. Ions combine together so that

their charges add to zero.

Ionic compounds are usually made of metal and non-metal ions.

Example:

NaCl – sodium chloride Fe2O3 – iron oxide CuSO4 – copper sulfate Ca3(PO4)2 – calcium phosphate

mnm m nm

Chemistry has its own language. Chemists communicate in this language to describe the millions of known compounds. This communication depends on a standard system of naming and writing the formulas for compounds. Chemists formed a group to standardize the system of naming and called themselves the International Union of Physical and Applied Chemists, or IUPAC.

A chemical formula is a shorthand method to represent compounds that uses the elements' symbols and subscripts. The chemical formula gives the following information:

• The different elements in the compound.• The number of atoms of each element in the compound.

Chemical Formulas

H2O

elementsymbols

subscript

• Subscript tells you amount of each element.• Water contains:

• 2 Hydrogen’s• 1 Oxygen

* No subscript indicates only 1 atom is present*

Ca3(PO4)2 • Contains 3 calcium atoms

*every subscript inside the brackets needs to be multiplied by 2*

P 1 atom x 2 = 2 phosphorus atomsO 4 atoms x 2 = 8 oxygen atoms

A binary compound contains 2 different kinds of elements. There can be more than one atom of each element in a binary compound. Binary ionic compounds usually contain one kind of metal ion combined with one kind of non-metal ion. Metal ions have positive charges and non-metal ions have negative charges.

Naming Binary Ionic Formula

When naming an ionic compound from its formula follow the rules below:

1. The cation (positive ion) is named first, followed by the anion (negative ion).

2. Write the full name of the metallic element (positive ion). 3. Write the name of the non-metallic element (negative ion) and

change the ending to "-ide".

Example: Write the name of NaCl.

Step 1: Name the first element.

Step 2: Name the second element and change the ending to "-ide".

The name of the compound is ________________________.

Na = sodium

Cl = chlorine chloridesodium chloride

Example: Write the name of Mg3P2.

Step 1: Name the first element.

Step 2: Name the root of the second element and add "-ide".

The name of the compound is ____________________________.

Mg = magnesium

P = phosphorus phosphide

magnesium phosphide

The following must occur when writing the formula for ionic compounds.

Writing Binary Ionic Formula

1. The formula must have the cation first, followed by the anion.2. The sum of the charges of the ions must be zero. That is, the

number of positive charges must equal the number of negative charges.

3. You may not change the charge of the ions to make the ion charges equal zero.

The "Criss-Cross" Method1. Write the ions and their charges side by side. 2. Make the number of the charge of one ion the subscript of

the other ion (omitting the + or – sign). Remember we do not write the number one as a subscript.

3. Reduce all subscripts to their simplest form, if necessary.

Example: Write the formula for aluminum oxide.

Step 1: Write the ions and their charges.

Step 2: Make the number of the charge of one ion the subscript of the other ion.

Example:Write the formula for barium fluoride.

Note: The charge on the fluoride ion is 1–. Since IUPAC rules do not write the number one as a subscript, we leave the barium without a subscript.

Al3+ and O2-

Al3+ O2-

Al2O3

Ba2+ F1-

BaF2

*Complete Ionic Compound Worksheet*

Some ions are composed of several atoms joined covalently. These are called polyatomic ions (poly = many).

Refer to the Periodic Chart of Ions for a list of ions.

The charge for polyatomic ions is for the whole group of atoms not just for the atom written last. DO NOT change the subscripts of polyatomic ions; if you change the subscripts you change the identity of these ions.

When indicating the presence of more than one polyatomic ion in a compound, we use parenthesis around the polyatomic ion, followed by its subscript. For example, the compound Al(CH3COO)3 has an aluminum ion and 3 acetate ions. Placing the acetate ion in parenthesis and following it with the subscript 3 indicates there are 3 acetate ions.

Polyatomic Ions

Example:Write the name for KNO3.

Step 1: Identify the cation.

Step 2: Identify the anion.

Step 3: Write the name of the cation first, followed by the anion.

K+ potassium ion

NO3- nitrate ion

potassium nitrateExample:Write the name of Hg2Cl2.




Hg22+ dimercury ion

Cl- chloride ion

dimercury chloride

Example:Write the name of Na3PO4.




Na+ sodium ion

PO43- phosphate ion

sodium phosphateExample: Write the name of NH4SCN.




NH4+ ammonium ion

SCN- thiocyanate ion

ammonium thiocyanate*Complete Polyatomic Compound Worksheet*

Ion Possible Ion ChargesCopper 1+, 2+

Iron 2+, 3+Cobalt 2+, 3+

Chromium 2+, 3+Lead 2+, 4+Tin 2+, 4+

Stock Naming SystemSeveral of the transition metals have more than one possible ion charge. They are often referred to as being multivalent. For example,

In 1919, Alfred Stock (1876 – 1946), a German chemist, suggested using numbers to indicate the charge of the ions. Prior to this the ions were given different names based upon their charge. The Cu+ ion was called cuprous and the Cu2+ ion was called cupric. However, the Fe2+ ion was ferrous and the Fe3+ ion was ferric. Since the charges were not always the same, the "–ic" and "–ous" suffixes caused some confusion. Today, the Stock naming system uses Roman numerals following the metal ion's name to indicate the ion's charge.

Example:

Copper (I) = Cu+ Copper (II) = Cu2+

Iron (II) = Fe2+ Iron (III) = Fe3+

cuprouscupric

ferrousferric

Example: Write the formula for iron (III) chloride

Step 1: Write out the ions.

Step 2: Criss-cross the charges.

Stock Naming

Example: Write the formula for lead (IV) sulfide.

Step 1: Write the ions.

Fe3+ and Cl-

FeCl3

Pb4+ and S2-

Pb2S4

*divide by GCF* Pb2S4 ÷ 2 PbS2

Writing the Chemical Formula

Example:Write the name for CoBr2.

Writing the Chemical NameWe name in a very similar manner as those ions with a single ion charge, except we must determine the charge on the metal ion.

CoBr2 Each Br is 1- total charge of 2- To make it neutral, Co has to be 2+

Cobalt (II) bromideExample:Write the name for MnO2.

MnO2 Each O is 2- total charge of 4- To make it neutral, Mn has to be 4+

Manganese (IV) oxide

*complete Stock Naming System Worksheet*

Covalent CompoundsNaming Covalent Compounds

Non-metals tend to combine chemically by sharing electron pairs. These bonds are known as covalent bonds. Neutral compounds made of atoms joined covalently are called molecular or covalent compounds.

We name covalent compounds differently than ionic compounds. We must indicate the number of each element by adding a prefix in front of the element's name.

Subscript Prefix Subscript Prefixone mono six hexatwo di seven hepta

three tri eight octafour tetra nine nonafive penta ten deca

Example:Write the name for CO2.

Step 1: Name the first atom with prefixes.

Step 2: Name the second element using prefixes and end in "-ide".

Step 3: Write the name of the compound writing the substance found more to the left on the periodic table first.

Naming Covalent Compounds

There is only 1 carbon. We omit “mono” for the first element.

carbon

There are 2 oxygen's, so we use the di prefix

dioxide

carbon dioxide

Example:Write the name for N2O4.

dinitrogen tetraoxide

Example:Write the name for PCl5.

phosphorus pentachloride

Note: There are several exceptions to the naming rules. Here are the common names for some of the compounds:

H2O = waterNH3 = ammoniaCH4 = methane

Writing formulas for covalent compounds involves the following rules: 1. Write the symbol for the first element followed by the subscript

indicated by the prefix.2. Write the symbol of the second element followed by the subscript

indicated by its prefix.

Writing Covalent Compound Formulas

DO NOT REDUCE THE SUBSCRIPTS!!!

Example:Write the formula for dinitrogen monoxide.

N2OExample:Write the formula for sulphur hexafluoride.

SF6

Example:Write the formula for phosphorus tribromide.

PBr3

Some elements do not exist as single atoms. These elements exist as pairs of atoms joined covalently, called diatomic molecules. The elements that exist as diatomic molecules are hydrogen (H2), oxygen (O2), fluorine (F2), chlorine (Cl2), bromine (Br2), iodine (I2) and nitrogen (N2).

When oxygen gas, hydrogen gas, etc. is used the formula will be O2, H2, etc.

Here is a mnemonic device to help you remember the diatomic molecules:

Diatomic Molecules

I Have No Bright Or Clever FriendsI = iodine H = hydrogenN = nitrogenBr = bromineO= oxygenCl = chlorineF = fluorine

QUIZ ON TUESDAY ON NAMING AND FORMULA WRITING

Chemical EquationsA chemical equation indicates the substances reacting and the substances produced in a chemical reaction. A chemical equation also shows the ratio in which these substances react or are produced.

A word equation can describe a chemical reaction.

Example:Hydrogen gas and oxygen gas react to form (or yield) water vapour.

A chemical equation can also show heat changes that occur.

2 H2(g) + O2(g) 2 H2O(g)

Endothermic reactions cause the reaction vessel to feel cooler because the reaction absorbs energy. The energy is used in the reaction, so energy is a reactant.

2 KClO3 + heat 2 KCl + 3 O2

2 H2(g) + O2(g) 2 H2O(g) + energy

Exothermic reactions release energy. Consequently, we consider heat or energy to be a product of an exothermic reaction.

SSymbol Meaning

+

(s)

(l)

(g)

(aq)

Recall:

and, reacts with, combines with, separates 2 or more reactantsyields, forms, makes, produces, separates reactants and productssolid state, precipitate, insoluble

liquid state

gaseous state, vapour

aqueous state (in water), dissolved in, soluble, in solution

Balancing Chemical EquationsExample:Balance the equation C3H8 + O2 CO2 + H2O

Example:Balance the equation Al2(SO4)3 + CaCl2 AlCl3 + CaSO4

* See white board*

* See white board*

* Complete Balancing Chemical Equations Worksheet*

Combustion ReactionsAre very rapid reactions of a hydrocarbon (fuel) substance with oxygen gas producing carbon dioxide and water plus a lot of heat.

General Formula: hydrocarbon + O2 CO2 + H2O

Example:CH4(g) (methane) + O2(g) CO2(g) + H2O(g)

Synthesis ReactionsInvolve the combining of smaller atoms/molecules into larger, more complex molecules. If only two different atoms appear on the reactant side, then the reaction must be synthesis.

General Formula: A + B AB

Example: Water and dinitrogen pentoxide gas react to produce aqueous hydrogen nitrate.

Types of Chemical Reactions

2 2

H2O (l) + N2O5 (g) 2 HNO3 (aq)

Decomposition ReactionsInvolve the splitting of large molecules into smaller molecules or elements.

General Formula: AB A + B

Example: Solid nickel (II) hydroxide decomposes to produce solid nickel (II) oxide and water.

Single Displacement (Replacement) ReactionsAre chemical changes that involve an element and a compound as reactants.

General Formula: A + BC B + AC

Example: Fluorine gas will react with sodium bromide in an aqueous solution to produce sodium fluoride and liquid bromine.

Ni(OH)2 (s) NiO (s) + H2O (l)

F2 (g) + 2 NaBr (aq) 2 NaF (aq) + Br2 (l)

switch

Double Displacement (Replacement) ReactionsOccur when elements in different compounds displace each other or exchange places. Generally, the reaction occurs in an aqueous system.

General Formula: AB + CD AD + CB

Example:When aqueous lithium iodide and aqueous silver nitrate react, they will produce solid silver iodide and aqueous lithium nitrate.

LiI (aq) + AgNO3 (aq) AgI (s) + LiNO3 (aq)

Acid-Base ReactionsWhen an acid and base react together, the reaction is known as a neutralization reaction. The products will always be water and a salt.

General Formula: ACID + BASE WATER + SALT

Example:When a solution of aqueous hydrochloric acid and solid potassium hydroxide react, water and aqueous potassium chloride are formed.

HCl (aq) + KOH (s) H2O (l) + KCl (aq)acid base water salt

Predicting Reaction Products When determining what the products will be in a chemical reaction, use the following information to help you. Synthesis ReactionReactants: Generally two elements or two compounds (where at least one compound is a molecular compound).Probable Products: A single compound

Decomposition ReactionReactants: Generally a single binary compound or a compound with a polyatomic ion.Probable Products: Two elements (for a binary compound), or two or more elements and/or compounds (for a compound with a polyatomic ion).

CombustionReactants: Oxygen and a compound of C, H, (O)Probable Products: CO2 and H2O

Single Replacement ReactionReactants: An element and a compound Probable Products: a different element and a new compound.

Double Replacement ReactionReactants: Two ionic compoundsProbable Products: Two new compounds

Determining the Physical States To determine if a product is a solid or not, use a table of solubility. The following are hints to help determine the physical state.

(s) – most metals, precipitates(l) – mercury, bromine, water(g) – noble gases, diatomic molecules (except bromine), ammonia(aq) – substance is in a water based solution (use solubility chart)

Isotopes

The number of neutrons in each atom varies, even between atoms of the same element. Potassium can exist as three different atoms. All three atoms contain 19 protons, but one potassium atom has 20 neutrons, another 21 neutrons and yet another has 22 neutrons.

Atoms that have the same number of protons but differ in their number of neutrons are called isotopes.

As you would expect, if different isotopes have different numbers of neutrons, they will have different masses. The mass number of an atom is the sum of the protons and neutrons found in the nucleus of that atom.

K3919 K39

If we look at the potassium isotopes above, the isotope containing 19 protons and 20 neutrons will have a mass number of ___________. We call this isotope potassium-39. The isotope that has 19 protons and 21 neutrons will have a mass number of ___________ and is called potassium-40.Chemists have designed a symbol for each isotope that includes the element’s symbol, its atomic number (Z) and its mass number (A).

The symbol for potassium-39 would be:

The symbol for potassium-40 would be:

19 + 20 = 39

19 + 21 = 40

K4019 K40

Atomic Mass

The masses of individual atoms are expressed as atomic mass units (amu) or µ. The atomic mass unit is defined as 1/12 the mass of a carbon-12 atom. This means a proton or a neutron has mass equal to approximately one atomic mass unit.

In many cases the amount of each isotope in the sample, or its relative abundance, can be determined using a mass spectrometer. The relative abundance of an isotope is the percent of each isotope found in an average sample of the element.

You have noticed that the atomic mass shown for each element on a periodic table is rarely a whole number. This is because it is actually an average mass of all isotopes of that element.

How to Calculate Average Atomic Mass

To determine the average atomic mass, you first need to determine what the mass contribution is for the isotope.

mass contribution = (mass)(relative abundance)

Once all the mass contributions have been determined, you simply add up the numbers to find your average atomic mass.

Relative Abundance of Stable Magnesium Isotopes

Isotope Relative Abundance (%)

Atomic Mass (amu)

Mg-24 78.70 23.98504Mg-25 10.13 24.98584Mg-26 11.17 25.98259

Example:Find the atomic mass of magnesium, using the information provided.

Recall, Avogadro’s Number relates the number of particles to mass. By definition, one mole of carbon atoms has a mass of 12.0000 g. If the mass of one mole of any atom is its atomic mass in grams, then

one mole of aluminum atoms has a mass of 27.0 gone mole of silver atoms has a mass of _____________ gone mole of sodium atoms has a mass of ____________ g,

One mole of any compound has a mass equal to its formula/molecular mass, in grams. Water has a molecular mass of 18.0 amu. The mass of one mole of water molecules is ____________ g.

The mass of one mole of a substance is called the molar mass (M). The units for molar mass are grams per mole (g/mol), so the molar mass of water is 18.0 g/mol.

Molar Mass

107.922.99

18.02

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Write formulas and names for ionic, polyatomic and covalent compounds using IUPAC nomenclature