Bonding and

Chemical Reactions

Part I

Bonding

I. What is a Compound?

A. Classification of Matter Review

• Elements = the simplest form of a pure substance

o______________________by physical or chemical

means

Examples: Sodium, Chlorine, anything on the PT

• Compounds = 2 or more _____________________

_____________________________________

o__________________or separated

_______________________

Examples: H2O, CO2, CH4

by chemical means only

Can be broken down

Cannot be broken down

different elements

chemically bonded in a fixed proportion

B. Compound Formulas

• Subscripts = tell you the # of each type of atom present in the

molecule

Example: CO2

# carbon atoms __ # oxygen atoms __

o If there are parentheses around two or more atoms, the subscript

applies to all atoms within the parentheses

Example: Al(CN)3

# aluminum atoms __ # carbon atoms __

# nitrogen atoms __

o If one of the atoms within the parentheses has a subscript, you

multiply this number by the number outside of the parentheses

Example: Fe2(SO4)3

# iron atoms __ # sulfur atoms __

# oxygen atoms ___

1 2

1

3

3

2 3

12

• Coefficients = the # in front that tells you how many total

molecules you have

Example: 3 BaCl2 means that I have 3 molecules of BaCl2.

Therefore it contains:

# barium atoms (Ba) ___

# chlorine atoms (Cl) ___

• Hydrates = a molecule with water surrounding it

Example: CuSO4 · 5 H2O

o Note—the dot in the hydrate formula does NOT mean

multiplication! It means “weakly bonded”

# Cu atoms ___

# S atoms ___

# O atoms ___

# H atoms ___

3

6

1

1

109

Checks for Understanding

Count the number of each atom in the compounds below

a. 3 H2O

# H_____ # O____

b. Na2(PO4)

# Na____ # P____ # O____

c. 2 Ca(NO3)2

# Ca____ # N____ # O____

d. CaCO3

# Ca____ # C____ # O____

6 3

2 1 4

2 4 12

1 1 3

II. Gram-Formula Mass• Gram-Formula Mass (GFM) = Mass of a compound

• To find the GFM, you add up the atomic masses of all of the elements in

the compound

o To find the atomic mass of an element, go to _______________

Examples:

a. H2O b. K2CO3

• To find the GFM of a hydrate, follow the same steps, being sure to include

the total mass of the water molecules

Examples:

a. CuSO4 · 5 H2O b. BaCl2 · 2 H2O

2 (1g) + 1 (16g) = 18 g 2 (39 g) + 1 (12 g) + 3(16 g) =

138 g

1 (64g) + 1 (32g) + 4 (16g) +

10 (1g) + 5 (16g) =

250 g

1 (137g) + 2 (35g) +

4 (1g) + 2 (16g) =

243 g

Periodic table

III. Percent Composition

• Think about this…

How would you find the percentage of boys in the classroom?

• Calculating the percent composition of elements in a

compound is the same idea except it looks at percentage in

terms of mass

• Percent Composition (by mass) = the percent of an

element in a compound, in terms of mass

o Equation: Table ________

# of boys (part)____

Total # of students (whole)x 100%

T

% Composition = mass of part x 100

by mass mass of whole

Examples:

1. A 14.80 g sample contains 3.83 g of iron and 10.97 g of

bromine. What is the percent composition of bromine?

2. Find the percent by mass of nitrogen in NH4NO3.

Step 1: Calculate the “part” = add up the total masses of the

N atoms

Step 2: Calculate the “whole” = calculate GFM

Step 3: Plug into equation

mass of part x 100 = 10.97 g Br x 100 = 74.12 %

mass of whole 14.80 g Sample

2 (14 g) + 4 (1 g) + 3 (16 g) = 80 g

% Composition = mass of part * 100 = 28 g N x 100 = 35 %

by mass mass of whole 80 g

2 N atoms (14 g) = 28 g of N

• To find the percent by mass of water in a hydrate, follow the same

steps, using the total mass of the water molecules as your “part”

Examples:

1. Find the percent by mass of water in BaCl2 · 2H2O

mass of part * 100 = 36 g H2O x 100 = 14.8%

mass of whole 243 g

Step 1: Calculate the “part” = add up the total mass of the

water molecules

Step 2: Calculate the “whole” = calculate GFM of hydrate

Step 3: Plug into equation

4 (1g) + 2 (16g) = 36 g of H2O

1 (137g) + 2 (35g) + 4 (1g) + 2 (16g) = 243 g of hydrate

2. 5.40g of BaCl2(s) hydrate was heated in a crucible. After heating

for 10 minutes, 4.64g of anhydrous BaCl2 remains. What is the %

by mass of water in the original sample of hydrate?

*Note – anhydrous/anhydrate means the substance without

water

Step 1: Calculate the “part” = mass of the water (mass of hydrate –

mass of anhydrate)

Step 2: Find the “whole” = the mass of the hydrate

Step 3: Plug into equation

5.40g – 4.64g = 0.76g of H2O

% Composition = mass of part * 100 = 0.76 g H2O x 100 = 14.1%

by mass mass of whole 5.40 g

5.40g

Checks for Understanding

1. Which species contains the greatest percent by mass of

hydrogen?

a. OH– b. H2O c. H3O- d. H2O2

2. 8.40g of CuSO4(s) hydrate was heated in a crucible. After

heating for 10 minutes, 5.38 g of anhydrous CuSO4 remains.

What is the percent composition by mass of water in the

hydrate?

A) 1/17 = 6 %

B) 2/18 = 11 %

C) 3/19 = 16 %

D) 2/34 = 6 %

36% H2O

IV. Introduction to Bonding

• Recall: A compound is defined as 2 or more different elements

chemically bonded together in a fixed proportion. So what is a

chemical bond and how and why do bonds form?

• Chemical bond = a force that holds elements together to form

compounds

o Force due the attraction between positive nuclei and negative

electrons

• Bonds form due to the ________ or ________ of

_______________ between atoms in order

____________________________ and ______________

o Recall: only _____________ valence electrons are involved

in bonding

Example:*Carbon has 4 unpaired valence

electrons so it can form ________

sharing transfer

valence electrons to achieve a full outermost shell become stable

lone, unpaired

4 bonds

Checks for Understanding

Draw the Lewis Dot Structures for the following elements

and identify how many bonds they could form

N

O

Ca

Cl

Ar

V. Types of Bonds

• There are 3 main types of bonds

1. Metallic

2. Ionic

3. Covalent

• The type of bond formed between atoms depends on two

things:

o The type of atoms involved (metals, nonmetals)

o The behavior of electrons

1. Metallic Bonds

• Type of atoms involved: two or more _______ (usually two

of the same metal i.e. _______)

• How the bond forms: metals share/make a _____________

____________

o The force of attraction between ___________________

and positively charged nuclei is what keeps the atoms

together

Why are the electrons “freely moving”?

Recall: metals want to lose electrons—this means

they don’t hold onto e- as tightly and the e- are able

to move from one atom to another

metals

Cu-Cu

sea of mobile

valence electrons

freely moving electrons

Properties:

https://www.youtube.com/watch?v=S08qdOTd0w0

Checks for Understanding

1. Conductivity in a metal results from the metal atoms having

a. high electronegativity

b. high I.E.

c. highly mobile protons in the nucleus

d. highly mobile electrons in the valence shell

2. Metallic bonding occurs between atoms of

a. sulfur b. copper c. fluorine d. carbon

1. ________________ of electricity and heat in ______ state

2. Malleable and ductile – can be “manipulated” without breaking

3. High melting and boiling points (see Table S)

4. __________ (can’t dissolve) in water

Good conductors solid

insoluble

2. Ionic Bonds

• Type of atoms involved : ________ and _________

• How the bond forms: metal _________________to the

nonmetal

o Results in the _______ becoming a ________ ion and

the _________ becoming a _________ ion. The force of

attraction between the oppositely charged ions is what

keeps the atoms together

Why does it make sense that the e- would behave this

way?

Metals want to lose e- to become stable;

nonmetals want to gain

• Salts are a type of ionic compound

Example: NaCl = classic table salt

metal

nonmetal

transfers electrons

metal positive

nonmetal

negative

Properties:

1. _________ electricity in _______ and ________

state (when dissolved in water)

2. Solid (hard) at room temperature

3. High melting and boiling points

4. ________ (dissolve in water)

*think of the properties of table salt (NaCl)

Conduct liquid aqueous

Soluble

• Ionic bonds can also involve a polyatomic ion

• Polyatomic ion = A covalently bonded (sharing electrons)

group of atoms that have a net electric charge (“fat chunks”)

• Found on Reference Table ______

Examples:

SO4-2 OH-1 NH4

+

Checks for Understanding

1. What occurs when potassium reacts with chlorine to form

potassium chloride?

a. Electrons are shared and the bonding is ionic.

b. Electrons are shared and the bonding is covalent.

c. Electrons are transferred and the bonding is ionic.

d. Electrons are transferred and the bonding is covalent.

E

Sulfate Hydroxide Ammonium

2. Which element reacts with oxygen to form ionic bonds?

a. Calcium c. Chlorine

b. Hydrogen d. Nitrogen

3. A solid substance is an excellent conductor of

electricity. The chemical bonds in this substance are most likely

a. ionic, because the valence electrons are shared between

atoms

b. ionic, because the valence electrons are mobile

c. metallic, because the valence electrons are stationary

d. metallic, because the valence electrons are mobile

3. Covalent Bonds

• Types of atoms involved: two or more ___________

• How the bond forms: nonmetals ________________in order to

achieve a stable arrangement of electrons

o The sharing of electrons creates a bond between the atoms

2 electrons shared = one bond

o Results in the formation of a molecule (also called

____________________)

Properties:

1. Does ____________electricity in any phase

2. Soft

3. Low melting and boiling points

4. __________________in water*SPLASH – Soft, Poor Conductor, Low MP/BP and water is an example!

nonmetals

share electrons

molecular compounds

not conduct

Sometimes soluble

Checks for Understanding

1. Which formula represents a molecular substance?

a. CaO

b. CO

c. Li2O

d. Al2O3

2. As a bond between a hydrogen atom and a sulfur atom is formed,

electrons are

a. shared to form an ionic bond

b. shared to form a covalent bond

c. transferred to form an ionic bond

d. transferred to form a covalent bond

3. Magnesium nitrate Mg(NO3)2 contains chemical bonds that are

a. covalent, only c. both covalent and ionic

b. ionic, only d. neither covalent nor ionic

Electronegativity’s Role in Bonding

• Recall: electronegativity is an atom’s desire for electrons

o It is on a scale from 0-4

o Metals have ____ electronegativity and nonmetals have _____

• Think about this…

• If ionic bonds exist between a metal and a nonmetal, why

does it make sense, in terms of electronegativity, that metals

transfer electrons to nonmetals?

• If covalent bonds exist between two nonmetals, why does it

make sense, in terms of electronegativity, that the nonmetals

share electrons?

B/c nonmetals have a higher desire for electrons (higher

electronegativity) so they “pull” electrons from the metals

B/c both nonmetals would have a high desire for electrons

so one wouldn’t “overpower” the other

Think of it like a tug-of-war for electrons!

low high

• The electron-dot diagram of a compound depends on the

type of bonding involved

• Recall: Only single, unpaired electrons can bond!

1. Ionic Compounds

• Recall: Ionic bonds form as a result of the metal transferring

electrons to the nonmetal.

• Steps for Drawing:

1. Draw the individual lewis dot diagrams for all the

elements in the compound

2. Draw the lone electrons from the metal(s) transferring to

pair up with the lone electrons of the nonmetal(s) (use an

arrow to show the transfer)

3. Redraw the compound with brackets and appropriate

new charges

VI. Lewis Dot Diagrams of Compounds

*Hint – it is just like drawing the lewis dot diagram of ions—

metals end up with 0 dots and a positive charge, nonmetals

end up with 8 dots and a negative charge

Example: NaCl

2. Covalent Compounds

• Recall: Covalent bonds form as a result of nonmetals

sharing electrons

• Steps for Drawing:

1. Draw the individual lewis dot diagrams for all the

elements in the compound.

*If there are more than 2 elements, the element with

the most unpaired valence electrons goes in the

middle*

2. Draw lines between elements connecting all the lone

electrons—the goal is to match up all the unpaired

electrons

*one line=one bond=2 electrons

Example: HBr

Checks for Understanding

For each of the following compounds, first identify the type of

bond present; then draw the appropriate lewis-dot diagram

1. CaO

2. CH4

3. O2

4. MgF2

VII. Naming Compounds • How you name a given compound depends on the type of bonding

present in the compound

1. Ionic Compounds

A) Chemical Formula Name

• If there are only 2 elements in the formula for the ionic compound,

follow the steps below to name it

Steps:

1. Write the name of the metal (*hint – the metal is written first)

2. Write the name of the nonmetal, drop the ending, add –ide.

Examples:

A) ZnO C) KCl

B) Ag2S D) Al2Br3

Zinc OxygenZinc Oxide

Silver Sulfur

Silver Sulfide

Potassium ChlorinePotassium Chloride

Aluminum Bromine

Aluminum Bromide

• If there are more than 2 elements in the formula for the

ionic compound, it typically means there is a polyatomic

ion involved. If that’s the case, follow the steps below to

name it

Steps:

1. Write the name of the metal

2. Use Table E and write the name of the polyatomic ion

as is

Examples:

A) Zn(OH)2 C) Ga(PO4)

B) AgCN D) Mg(ClO3)2

Zinc Hydroxide

Silver Cyanide

Gallium Phosphate

Magnesium Chlorate

B) Name Chemical Formula

• When writing the formula for ionic compounds, it is

important to remember that ___________ are

electrically _______. That means all the ________ of

the ions in an ionic compound must cancel out or

______________.

• To determine this, use the element’s oxidation number

oOxidation Number = the number of electrons lost or

gained by an atom

Found ________________ in the

______________

neutralcompounds

charges

add up to zero

on Periodic Table

top right corner

• To ensure that the charges add up to zero, there is a trick

called the “criss-cross” method

o “Criss-cross” Method = a shortcut where you criss-

cross the oxidation numbers to determine how many

atoms of each element must be in the compound to

make the compound neutral.

Helps determine the subscripts on each element so

that the total sum of the charges = 0

Examples:

A) Al+3 and S-2 B) Co3+ and Sulfate (SO4)2 -

Al2S3

2(+3) + 3(-2) = 0

• This trick can be used to help with writing the formulas of ionic

compounds

Co2(SO4)3

2(+3) + 3 (-2) = 0

• To write chemical formulas for ionic compounds,

follow the steps below

Steps:

1. Write the symbol of the metal with its oxidation

number (remember, found in the upper right-

hand corner of PT)

2. Write the symbol of the nonmetal with its

oxidation number (choose the 1st one)

3. If the charges cancel each other (add up to zero)

then simply combine the two symbols

4. If the two charges DO NOT cancel each other

out, use the “criss-cross” method—the charges

cross down and become subscripts

Examples:

A) Sodium Sulfide C) Aluminum Oxide

B) Magnesium Fluoride D) Calcium Oxide

Na2S

MgF2

Al2O3

CaO

Na1+S2-

Mg2+F1-

Al 3+O 2-

Ca +2O 2-

2. Covalent (Molecular) Compounds

• With covalent compounds, prefixes are used to describe

how many of each atom are present

A) Chemical Formula Name

1. Name the first nonmetal. If there is more than one atom of

it (if there is a subscript), put the correct prefix in front of it.

The first element only gets a prefix if there is more than

one

2. Name the second nonmetal, drop the ending, add –ide.

Place the correct prefix in front of it. The second element

ALWAYS gets a prefix

Examples:

A) CO B) CO2 C) N2O3

B) Name Chemical Formula

1. Write the chemical symbol of the elements

2. Use the prefixes to tell you how many there are of each

element. Write the number as a subscript. *Remember, if

there is no prefix on the first element, it’s because there

is only one and no subscript is needed.

Examples:

A) Diphosphorous pentoxide

B) Phosphorous tetrafluoride

Carbon Monoxide Carbon dioxide Dinitrogen trioxide

P2O5

PF4

Part 2

Chemical Reactions

I. What is a Chemical Reaction?

Review of Types of Changes

• Remember there are two types of changes that matter can

undergo

1. Physical Change = a change that DOES NOT change the

chemical nature of a substance; _____________________

___________________

Examples:

2. Chemical Change = a change that DOES change the

chemical identity of a substance; _____________________

_______________________________

Examples:

appearance changes but

not chemical identity

any phase change (boiling,

melting, freezing), the act of dissolving

new substances are

formed with new chemical make-up

burning, rusting, reacting

Chemical Reactions

• The main example of a chemical change is a chemical reaction

oChemical Reaction = when one or more substances _____________________________

oA chemical reaction involves substances called reactants forming new substances called products. The reactants “react” to “produce” the products.

Example:

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

• How do you know if a chemical reaction happened? Remember, there are certain signs to look for:

1.Color change (an obvious one)

2. Bubbling/fizzing

3. Change in temperature

4. Formation of a precipitate (a solid “falls out” of a solution)

Reactants yields Products

Physical state of substances

change into new substances

• How do chemical reactions happen? There are certain conditions

that must be met. Think of kicking a field goal. To get a field

goal, 2 things must happen:

1. Proper placement

2. Enough power

The same idea is true for a chemical reaction!

o Collision Theory = theory that it is the

_________________________that allow a reaction to occur

In order for a reaction to occur, the collisions must be

________________. They must have:

1. Proper _____________________

• If they don’t collide in the correct way, no reaction

will occur

2. Enough ______

• If the collisions are too slow, or the particles don’t

have enough force behind them, no reaction will

occur

collisions between reactants

effective collisions

orientation (positioning)

energy

• How can you speed up the rate of a chemical reaction, or in other

words, what factors affect the rate of collisions?

1. Concentration (the number of particles per volume) – If the

____________ of the reactants _________, then the

______________________

o More particles in a given space = more collisions

*Hint – think of adding more people to our classroom

As concentration _________, number of collisions __________, and the

reaction happens ______

2. Surface Area (how spread out the particles are) – If the

___________ of the reactants __________, then the

_____________________

*Hint – think of crushed up alka seltzer vs. a tablet

As surface area ___________, the number of collisions _________, and

the reaction happens ________

II. Rates of Chemical Reactions

concentration increases

reaction will occur faster

increases

increases

faster

increases

increasesfaster

surface area

reaction will occur faster

increases

3. Temperature- If the ___________ of the reactants __________,

then the ______________________

*Hint – think of the alka seltzer in warmer water vs. colder water

As temperature _________, the number of collisions _________, and

the reaction happens ________

4. Catalyst – If a _______ is added to a reaction, then the

______________________

o A catalyst speeds up a reaction by ________ the amount of

______ it takes _______________; particles need less energy to

react so they can react faster

*Hint – think of a catalyst as a short cut home from school

When a catalyst is added, the energy it takes for a reaction to start

________, so the reaction happens______

temperature increasesreaction will occur faster

increasesfaster

increases

catalystreaction will occur faster

reducing

energy to start a reaction

fasterdecreases

Checks for Understanding 1. In order for a reaction to occur there needs to be effective collisions

between reactant particles. What are the two things needed for a collision

to be effective?

a.

b.

2. When the amount of EFFECTIVE collisions increases, what happens to the

rate of reaction?

3. Milk contains the sugar lactose. Over time, a chemical reaction occurs.

Lactose changes to lactic acid, which makes the milk taste sour.

Reaction: lactose + O2 lactic acid

Based on collision theory, why do we keep milk in the refrigerator?

How to Speed Up Chemical Reactions (and get a date) Video Clip

Enough energy

Proper orientation

increases – the reaction happens faster

Because decreasing the temperature decreases the number of

collisions, which makes the reaction happen slower

III. Balancing Chemical Reactions

• Subscripts and coefficients are also parts of a chemical reaction

o Recall: subscripts tell you how many atoms of a particular element are

in a molecule and coefficients tell you how many total atoms/molecules

are present

• Subscripts and coefficients are significant because a chemical reaction

must obey the Law of Conservation of Mass

o Law of Conservation of Mass = matter/mass cannot be created or

destroyed

• This means:

1. The total mass you started with must equal the total mass you

end up with

Example: Using the equation above, what is the mass of H2O

produced when 320 grams of H2 reacts completely with 40

grams of O2? 360 grams of H2O

2.The total number of atoms of each element must be the

same on both sides of the equation

• To accomplish this, we must make sure chemical

reactions are balanced

*Think of chemical reactions like recipes. The reactants are

the ingredients and the products are the finished dish.

When you add ¾ cups of chocolate chips to make chocolate

chip cookies, there are still ¾ cups of chocolate chips in the

cookies when the recipe is complete!*

How to balance chemical equations

• Coefficients are used to balance the number of atoms of each element on

both sides of the reaction.

o Must be a whole number

o Must be as reduced as possible

Important Note* – Coefficients can be changed, subscripts cannot!

Examples:

1) ____ HCl (aq) + ____ Zn (s) ____ H2(g) + ____ ZnCl2(aq)

Reactants Elements Products

H

Cl

Zn

2 1 1 1

2) _____ N2 + _____ H2 _____ NH3

3) _____ Al2O3 _____ Al + ____ O2

Elements

1 3 2

2 4 3

4) _____ Al + _____ Br2 _____ AlBr3

5) _____ AlBr3 + ___ Cl2 _____ Al Cl3+ ____ Br2

2 3 2

2 3 2 3