INTRODUCTION TO CHEMISTRY 30 Slide 2 COMPONENTS OF AN ATOM- The
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.
Slide 3 ATOM REVIEW 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. 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. Slide 4 CHARACTERISTICS OF THE ATOM The number of
protons in the nucleus of an atom is termed its 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 Slide 5 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. Slide 6 Another characteristic of an
atom of an element is it's atomic 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. Slide 7 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. Slide 8 ASSIGNMENT
Components of the atom Slide 9 NAMING COMPOUNDS Covalent compounds-
(contain nonmetal atoms combining with other nonmetal atoms)
Electrons are shared between atoms 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. Slide 10 HYDROCARBONS
(STRAIGHT CHAINED) Hydrocarbons are compounds that contain only
carbon and hydrogen. (C n H 2n ) 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 1meth - 2eth - 3prop - 4but - Slide 11 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 Alkaneall
single- aneC n H 2n+2 Alkeneone double- eneC n H 2n Alkyneone
triple- yneC n H 2n-2 Slide 12 Assignment: naming covalent
compounds Slide 13 Ammonium (NH 4 +) compounds Ammonium compounds
contain the complex cation NH 4 +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. FormulaName (NH 4 ) 2 SO 4 Ammonium sulfate
(NH 4 ) 3 PO 4 Ammonium phosphate Slide 14 MONOVALENT IONIC CATIONS
Ionic compounds containing monovalent cations (cation with one
charge) To Name (using a table of ions):(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. FormulaName AgClSilver chloride Mg(NO 3 ) 2 Magnesium
nitrate Slide 15 DIVALENT CATIONS Ionic compounds containing
divalent cations (metal ions with two possible charges) To Name
using given the formula: Locate the name of the anion and cation in
a table of ions or periodic table. 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 Fe 2
O 3 O 2- 2 Slide 16 EXAMPLES Find the charges on the cations: FeO-
NiF 2 Slide 17 To determine name then we: Name the cation Determine
the charge on the cation using the method above. Apply the correct
Roman Numerals Finally name of the anion Formula Name of Cation
Total Charge on Anion Total charge on Cation Charge on Cation Name
Cu 2 OCopper-2+2+1Copper (I) oxide CrCl 3 Chromiu m -3+3 Chromium
(III) chloride Slide 18 EXAMPLES TiC-PbO 2 - Assignment: naming
ionic compounds Slide 19 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. Slide 20 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 Slide 21 GRAM MOLECULAR WEIGHT (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) Na122.99 Cl135.45 Gram Molecular
weight ( Molar Mass ) ; 1 mole = 58.44 g/mol Slide 22 Element
Number of Atoms Atomic Weight (g/mol) Total weight (g/mol) C112.01
H41.014.04 Molar Mass =16.05 g/mol Example: CH 4 Slide 23 Example
Ca(NO 3 ) 2 Assignment: Molar Mass sheet Element Number of Atoms
Atomic WeightTotal weight Ca140.08 N214.0128.02 O616.0096.00 Gram
Molecular weight ( Molar Mass ) ; 1 mole = 166.10 g Slide 24
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 Slide 25
STEPS: 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** Slide 26 EXAMPLES 1.
Calculate the mass in grams of 35 moles of CaCO 3. Given
information is 35 moles of CaCO 3. Asked to calculate the mass in
grams. The mole triangle indicates that you should multiply the 35
moles by the molar mass of CaCO 3 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 1 mole = 100.09 g/mole Step 2; Calculation of
Answer 35 moles * 100.09 g/mol = 3503.15 g Slide 27 Calculate the #
of molecules in 820 L of SO 2 (g) given off by a chemical plant at
STP. The given information is 820 L of SO 2 (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 / 25.4 L/mol. = 32.28 mol. Step
2; Calculation of Answer 32.28 mol. * 6.023 *10 23 p/mol. = 1.9 *10
24 particles Slide 28 Assignment: Mole Calculations Slide 29 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:
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.
Slide 30 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. Slide 31 DETERMINE THE # OF ATOMS OF EACH
TYPE PRESENT IN THE FOLLOWING REACTANTS. Reactants# of each atom
PbS + 2 PbO Pb = S = O = Ca(NO 3 ) 2 + 2 KOH Ca = N = O = K = H = 2
NH 4 NO 3 + H 2 S N = H = O = S = Fe(NO 3 ) 3 + 3 LiOH Fe = N = O =
Li = H = Ca 3 (PO 4 ) 2 + 3 H 2 SO 4 Ca = P = O = H = S = Slide 32
BALANCING 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: Reactant Product
___C 3 H 8 (g)+ ___O 2 (g)___CO 2 (g) + ___H 2 O (g) Step 1 Balance
atoms that appear only once first (C and H ) _1_C 3 H 8 (g)+ ___O 2
(g) _3_CO 2 (g) + _4_H 2 O (g) Step 2 Balance atoms that appear
more than once last (O) _1_C 3 H 8 (g)+ _5_O 2 (g) _3_CO 2 (g) +
_4_H 2 O (g) Slide 33 Balance polyatomic ions as a group, for
example SO 4 2- ion. Caution: The ion must remain the same in
reactant and product. Example #2: Reactant Product ___Ca(NO 3 ) 2
(aq) + ___Na 3 PO 4 (aq)___Ca 3 (PO 4 ) 2 (s) + ___NaNO 3 (aq) Step
1 Balance atoms that appear only once ( Ca, Na ) _3__Ca(NO 3 ) 2
(aq) + ___Na 3 PO 4 (aq) ___Ca 3 (PO 4 ) 2 (s) + _3__NaNO 3 (aq)
Step 2 Balance atoms in ions as groups (PO 4 ; NO 3 ) _3__Ca(NO 3 )
2 (aq) + _2__Na 3 PO 4 (aq) _1__Ca 3 (PO 4 ) 2 (s) + _6__NaNO 3
(aq) Slide 34 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: Reactant Product ___CuFeS 2 (s) + ___O 2 (g)___Cu (s) +
___FeO (s) + ___SO 2 (g) Step 1 Balance atoms that appear only once
first _1_CuFeS 2 (s) + ___O 2 (g) _1_Cu (s) + _1_FeO (s) + _2_SO 2
(g) Step 2 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_CuFeS 2 (s) + _5_O 2 (g)_2_Cu (s) + _2_FeO (s) + _4_SO 2
(g) Slide 35 Assignment: Balancing equations worksheet Slide 36
STOICHIOMETRY Chemical reactions are like the recipe for the
cookies. The balances in the equations are mole recipes that tell
us the # of moles that react and form. Example: Notice that all of
the values in the table are in the same ratio as the balance in the
equation. C 3 H 8 : O 2 is always 1 : 5, CO 2 : H 2 O 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 Equation (balanced) _1_C 3 H 8 (g) + _5_O 2 (g) _3_CO 2 (g) +
_4_H 2 O (l) If we had 2 moles of C3H8 (g) then 2 moles 10 moles 6
moles 8 moles Slide 37 Moles of ------>C 3 H 8 (g)O 2 (g)CO 2
(g)H 2 O (l) Complete the rest of this table using the equation
above 12 moles 2 moles 0.5 moles 5 moles Slide 38 MOLE TO MOLE
STOICHIOMETRY The following technique can be used to predict the #
of moles that will react or form in an equation. Identify the given
number of moles. Identify the balance of the Given. Identify the
balance of the substance you wish to find Multiply. Moles of Known
(n)X Balance of Unknown Balance of Known =Moles of unknown (n)
Slide 39 Example: Using the balanced equation below, predict 1. The
number of moles of C 3 H 8 (g) that reacts to produce 8.4 moles of
CO 2 (g). Equation (balanced)_1_C 3 H 8 (g)+_5_O 2 (g) _3_CO 2 (g)
+ _4_H 2 O (l) 8.4 moles of C 3 H 8 (g)X 3 CO 1 C 3 H 8 =25.2 moles
CO 2 (g) Slide 40 The number of moles of H 2 O (l) that form if
63.7 moles of O 2 reacts. Answer: 63.7 moles O 2 (g)X 4 H 2 O (l) 5
O 2 (g) = 51.0 moles H 2 O (l) Slide 41 Assignment: Mole to Mole
stoichometry Slide 42 MASS TO MASS We can use a simple 3 step
method to solve stoichiometric questions with balanced equations.
Identify the given and convert it to moles. Identify the desired,
and multiply the given number of moles by the mole ratio to produce
moles of desired substance. Convert moles of desired substance to
the units asked for in the question. Example: Slide 43 What mass of
methane gas in grams must burn to produce 365 grams of water, by
the following chemical reactions ? Given is 365 g of water.
Calculate moles of water. Identify desired; mass of Methane gas.
Multiple by mole ratio _1_CH 4 (g)+_2_O 2 (g)_2_H 2 O (g)+_1_CO 2
(g) 365 g 18.02 g/mol=20.25 mol 20.25 mol H 2 O (l)X1 CH 4
(g)=10.13 mol CO 2 (g) 2 H 2 O (g) Slide 44 Convert moles of
desired to the units asked for in the question: Mass of Methane
gas. Assignment: Mass to Mass Stoichiometry 10.13 mol CO2X44.01
g/mol=446 g
