Chem. 30- Introduction Unit
1. Components of an AtomThe modern atom as viewed by scientists today consists of three main particles located in two regions.

The first of these two regions is the nucleus, or central core of the atom which is composed of positively charged protons
and neutrons with a neutral charge.
o
It is believed that the neutrons are needed to hold the positively charged protons together in the nucleus. The
force that holds these particles together is termed the nuclear binding force and it is believed to be one of the
strongest forces that exists in nature.
o
The nucleus takes up a very small portion of the atom. If the atom was the size of a football field the nucleus
would be the size of a household fly on the 55 yard line.

The second region surrounds the nucleus and is termed an electron cloud. The cloud holds the third particle which is a
negatively charged electron.
Characteristics of the Atom1. The number of protons in the nucleus of an atom is termed it's atomic number. This number is distinctive
(characteristics) for the atoms of each element (it can be found on the periodic table).
Atomic Number = # of protons
2. The number of neutrons in the nucleus of an atom is not distinctive and may vary. This creates varieties of atoms we call
isotopes. Isotopes are atoms of the same element with different numbers of neutrons.
3. Another characteristic of an atom of an element is it's atomic mass (mass #). Protons and Neutrons have approximately the
same mass, while electrons have very little mass in comparison to either Protons or Neutrons. The atomic mass is therefore
determined from the number of protons and neutrons. It is often called the mass number (#).
Mass # (Atomic Mass) = # of Protons + # of Neutrons.
Since atoms of an element always have the same number of protons, isotopes are atoms of the same element with
different mass numbers.
4. The number of electrons in a neutral atom (no charge) is equal to the number of protons (atomic #). Atoms may either
gain or lose electrons during chemical interactions with other atoms. If they gain electrons they become negatively charged, if
they lose electrons they become positively charged. We term these charged atoms ions.
For Example: If Magnesium loses two electrons it would have 12 + charged protons and only 10 - charged electrons and would
become a +2 ion. If Chlorine gains one electron it would have 35 protons (+) and 36 electrons (-) and become a - 1 ion. The
charge on the ion indicates the number of electrons gained or lost.
2.
Naming Compounds
Covalent compounds(contain nonmetal atoms combining with other nonmetal atoms)
1. Binary Molecular Compounds
To Name:

The first atom is named in full

The second atoms name is shortened and -ide added.

The prefixes below are added to the first and second name to indicate the number of atoms present in the compounds.

The prefix mono is typically not placed on the first atoms name.
2.
# of Atoms
Prefix
# of Atoms
Prefix
1
mono-
6
hexa-
2
di-
7
hepta-
3
tri-
8
oct-
4
tetra-
9
non-
5
penta-
10
dec-
Examples:
P2O5 -diphosphorus pentaoxide
CO2 -carbon dioxide
Hydrocarbons(straight chained)
Hydrocarbons are compounds that contain only carbon and hydrogen.
To Name:
 The first part of the name is a prefix that indicates the number of carbon atoms. The prefixes are the same as
those used by Binary Molecular compounds above except for the first four. These four are:

# of Carbon Atoms
Prefixes
1
meth -
2
eth -
3
prop -
4
but -
The second part of the name is a suffix that describes if the compound contains single bonds, a double or a triple bond
between the carbon atoms. The following table illustrates the naming and gives examples.
Group
Bonds between carbons
Suffix
Ratio of Carbon to Hydrogen
Example
Name
Alkane
all single
- ane
CnH2n+2
C3H8
propane
Alkene
one double
- ene
CnH2n
C4H8
butene
Alkyne
one triple
- yne
CnH2n-2
C5H8
pentyne
Naming ionic compounds(contain a metal or NH4 + ion)
1.
2.
Ammonium (NH4 +) compounds
Ammonium compounds contain the complex cation NH4 +1.
To Name: (using a table of ions)
 The first part of the name is Ammonium
 Second part of name is the name of the anion.
Formula
Name
(NH4)2SO4
Ammonium sulfate
(NH4)3PO4
Ammonium phosphate
Monovalent Cations
Ionic compounds containing monovalent cations (cation with one charge) are named by simply listing the name of the cation and
the name of the anion.
To Name (using a table of ions):
 Locate the name of the metal cation (positive ion). Make sure it has only one charge.
 Locate the name of the anion.
 Place names together.
Formula
Name
AgCl
Silver chloride
Mg(NO3)2
Magnesium nitrate
3. Divalent cations
Ionic compounds containing divalent cations (metal ions with two possible charges) can be named in two ways

The Roman Numerals is equal in value to the charge on the cation.
Cation
Name
Sn 4+
Tin (IV)
Cu+
Copper (I)
To Name using given the formula:
o Locate the name of the anion and cation in a table of ions.
o Using the concept that the total charge of the anion and cation must be equal we can determine what the charge
on the cation must be. ( anion charges are always fixed.) See example below
Formula
Charge on Anion
Total charge on
anion
Total charge on
Cation
Number of Cations
Charge on Each Cation
Fe2O3
O 2-
-6
+6
2
+3

The name of the example above would be: Iron (III) oxide
To determine name then we: (using a table of ions)
1. Name the cation
2. Determine the charge on the cation using the method above.
3. Apply the correct Roman Numerals
4. Finally name of the anion.
Formula
Name of Cation
Total Charge on
Anion
Total charge on
Cation
Charge on Cation
Cu2O
Copper
-2
+2
+1
CrCl3
Chromium
-3
+3
+3
Name
Mole Theory- Definition: The mole is defined as the atomic or molecular weight of a substance expressed in grams. It is a metric
unit for amount of substance and has the abbreviation mol.
One mole of a substance then is the atomic weight of the element expressed in grams.

The number of particles in this amount is termed Avogadro's Number and has been estimated at
6.023* 10 23
particles.

Whenever we have Avogadro's number of particles in a sample we have one mole.

To give you a sense of it's size, imagine that each particle in a mole was a piece of paper. If we were to stack this
paper one sheet on top of another, a mole of paper would stretch from the surface of the earth to the planet Pluto.
7. Molar Mass
To calculate the gram molecular weight of a substance made up of more than one element (compound), we add up the atomic weights
of the elements that comprised the compound. Atomic weights are listed in the periodic table.
Example: NaCl
Element
Number of Atoms
Atomic Weight (g/mol)
Total weight (g/mol)
Na
1
22.99
22.99
Cl
1
35.45
35.45
Gram Molecular weight ( Molar Mass ) ; 1 mole =
58.44 g/mole
Example: CH4
Element
Number of Atoms
Atomic Weight
(g/mol)
Total weight
(g/mol)
C
1
12.01
12.01
H
4
1.01
Molar Mass =
4.04
g/mol
Example: Ca(NO3)2
Element
Number of Atoms
Atomic Weight
Total weight
Ca
1
40.08
40.08
N
2
14.01
28.02
6
16.00
96.00
O
Gram Molecular weight ( Molar Mass ) ; 1 mole =
g
Assignment: Molar Mass sheet
8. Calculations with the Mole
The mole has three values that can be used to do calculations with the mole. They are:
 mass
 volume (one mole in the gas state at 0 C and 100 kPa.(called standard temperature and pressure STP = 24.5 L.)
 # of particles
Steps:
1.
2.
3.
4.
Write down the given information.
Write down what you are trying to find.
Use the mole triangle to determine what operation you will perform.
Complete all required calculations and write down the final answer- **be sure to include units**
Examples
1. Calculate the mass in grams of 35 moles of CaCO3.
 Given information is 35 moles of CaCO3.
 Asked to calculate the mass in grams.
 The mole triangle indicates that you should multiply the 35 moles by the molar mass of CaCO3
Step 1; Calculation of molar mass
1 * 40.08 g/mole = 40.08 g
1 * 12.01 g/mole = 12.01 g
3 * 16.00 g/mole = 48.00 g
Step 2; Calculation of Answer
35 moles *
=
g
1 mole =
2. Calculate the # of molecules in 820 L of SO2 (g) given off by a chemical plant at STP.
 The given information is 820 L of SO2 (g) at STP.
 Information you are asked to find is the # of particles.
 The mole triangle indicates that you should divide 820 L by the molar volume to calculate moles
 then multiply the moles by 6.023 * 10 23 p/mol.
Step 1;Calculation of moles
820 L / 22.4 L/mol. =
mol.
Step 2; Calculation of Answer
* 6.023 *10 23 p/mol. =
particles
Assignment: Mole Calculations
9. Word and formula equations
1. Two types of equations are written by chemists:
 word equations: describe the substances that react in a chemical reaction (termed reactants), and the products
that are formed, along with their states
 formula equations are a shorthand method used to describe the same reactions. These are of two types:
o Skeleton equations: (unbalanced) which lists the correct formula of each reacting substance and
product substances, and their states.
 Balanced equations: which list the correct formulas, states and balances the equation for the
number of atoms present. That is it takes into account the Law of Conservation of Mass, and makes
sure there is the same number and type of atom in the reactant and product. In Chemistry 30 we
should only use balanced equations.

We balance equations by changing the coefficients or numbers in front of the substance.
WE NEVER CHANGE THE FORMULAS OF SUBSTANCES IN ORDER TO BALANCE.

Counting the atoms correctly is therefore critical. The balance (coefficient) we use is always multiplied by the subscripts
used in each formula, to indicate how many atoms are represented. If atoms are in two different reactant or product
compounds, they are added together to determine how many are present in total.
Determine the # of atoms of each type present in the following reactants.
Reactants
# of each atom
Pb =
PbS + 2 PbO
S=
O=
Ca =
N=
Ca(NO3)2 + 2 KOH
O=
K=
H=
N=
2 NH4NO3 + H2S
H=
O=
S=
Fe =
N=
Fe(NO3)3 + 3 LiOH
O=
Li =
H=
Ca =
Ca3(PO4)2 + 3 H2SO4
P=
O=
H=
S=
11. Balancing by Inspection
Balancing equations is basically a process of trial and error, called inspection, but a few hints can help.
1. Balance atoms that appear only once in reactant and product first, and atoms that appear more than once last.
Example #1:
Step 1
Step 2
Reactant
Product
___C3H8 (g)+ ___O2 (g)
___CO2 (g) + ___H2O (g)
Balance atoms that appear only once first (C and H )
_1_C3H8 (g)+ ___O2 (g)
_3_CO2 (g) + _4_H2O (g)
Balance atoms that appear more than once last (O)
_1_C3H8 (g)+ _5_O2 (g)
_3_CO2 (g) + _4_H2O (g)
2. Balance polyatomic ions as a group, for example SO4 2- ion. Caution: The ion must remain the same in reactant and product.
Example #2:
Step 1
Step 2
Reactant
Product
___Ca(NO3)2 (aq) + ___Na3PO4 (aq)
___Ca3(PO4)2 (s) + ___NaNO3 (aq)
Balance atoms that appear only once ( Ca , Na )
_3__Ca(NO3)2 (aq) + ___Na3PO4 (aq)
___Ca3(PO4)2 (s) + _3__NaNO3 (aq)
Balance atoms in ions as groups (PO4 ; NO3 )
_3__Ca(NO3)2 (aq) + _2__Na3PO4 (aq)
_1__Ca3(PO4)2 (s) + _6__NaNO3 (aq)
3. In some cases the # of atoms of an element in the reactants may be odd, while the # in the products will always be even (due to a
even subscript). In this case you need to double the balance of all atoms already balanced and continue the balancing.
Example #3:
Step 1
Step 2
Reactant
Product
___CuFeS2 (s) + ___O2 (g)
___Cu (s) + ___FeO (s) + ___SO2 (g)
Balance atoms that appear only once first
_1_CuFeS2 (s) + ___O2 (g)
_1_Cu (s) + _1_FeO (s) + _2_SO2 (g)
Balance oxygen now. Notice that there is five atoms in the
products but the reactants will always be even. To balance,
double all balances already made. Now continue by balancing
the oxygen
_2_CuFeS2 (s) + _5_O2 (g)
_2_Cu (s) + _2_FeO (s) + _4_SO2 (g)
Assignment: Balancing equations worksheet
13. Mole recipes
Example:

Equation (balanced)
_1_C3H8 (g)
If we had 2 moles of C3H8 (g) then
2 moles
+
_5_O2 (g)
_3_CO2 (g)
10 moles
6 moles
+
8 moles
Notice that all of the values in the table are in the same ratio as the balance in the equation. C 3H8 : O2 is always 1 : 5, CO2 : H2O
is always 3: 4 . We call these ratios, equation factors or mole ratio. The reactants and products in this equation always react
and form in these
Moles of ------>
C3H8 (g)
O2 (g)
CO2 (g)
H2O (l)
12 moles
2 moles
Complete the rest of this table using the equation above
0.5 moles
5 moles
_4_H2O (l)
14. Mole to Mole Stoichiometry
The following technique can be used to predict the # of moles that will react or form in an equation.
Balance of Unknown
Moles of Known (n)
X
=
Moles of unknown (n)
Balance of Known
Example:
Using the balanced equation below, predict
1. The number of moles of C3H8 (g) that reacts to produce 8.4 moles of CO2 (g).
Equation (balanced)
_1_C3H8 (g)
+
_5_O2 (g)
_3_CO2 (g)
+
Answer:
3 CO
8.4 moles of C3H8 (g)
X
=
25.2 moles CO2 (g)
1 C3H8
2. The number of moles of H2O (l) that form if 63.7 moles of O2 reacts.
Answer:
4 H2O (l)
63.7 moles O2 (g)
X
=
51.0 moles H2O (l)
5 O2 (g)
Assignment: Mole to Mole stoichometry
15. Mass to Mass Mole Method
We can use a simple 3 step method to solve stoichiometric questions with balanced equations
1. Identify the known and convert it to moles.
2. Identify the unknown, and multiply the given number of moles by the mole ratio to produce moles of unknown substance.
3. Convert moles of unknown substance to the units asked for in the question.
Example: What mass of methane gas in grams must burn to produce 365 grams of water, by the following chemical reactions ?
_1_CH4(g)
+
_2_O2(g)
_2_H2O (g)
+
_1_CO2(g)
1. Given is 365 g of water. Calculate moles of water.
365 g ÷18.02 g/mol
=
20.25 mol
2. Identify unknown; mass of Methane gas. Multiple by mole ratio
20.25 mol H2O (l)
X
1 CH4 (g)
=
10.13 mol CO2 (g)
2 H2O (g)
3. Convert moles of unknown to the units asked for in the question: Mass of Methane gas.
10.13 mol CO2
X
44.01 g/mol
=
446 g
_4_H2O (l)