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Classification of Matter
PURE SUBSTANCE: ELEMENT: COMPOUND: MIXTURE: SOLUTIONS: MECHANICAL MIXTURE:
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He
Elements and the Periodic
Table: A Review
The Elements All matter is made up of atoms
of various elements. There are 109
elements known to date. Every
element has a unique set of physical
and chemical properties that make it
different from the rest. Every
element has a unique:
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Grouping of Elements on the
Periodic Table The Periodic Table was derived by a
Russian scientist named
_________________________________
who spent his life’s work studying properties
of elements.
Elements on the PT are subdivided:
groups
periods
Metals
Non – metals
Metalloids
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H O C 1
1 6
12 8
16
Bohr-Rutherford Diagrams Recall:
A Bohr-Rutherford (B/R) diagram is used to represent the
electron configuration of an atom of any element. The
following information is required on all B/R diagrams.
1. Number of Electrons:
2. Number of Protons:
3. Number of Neutrons:
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Predicting Chemical Reactivity The outermost energy level of an atom
(____________________) will tell us a lot about the
element’s chemical reactivity. Elements with 8 electrons in
their outer energy level appear to have a special
significance. They are essentially non-reactive and are
considered stable. We call this the Stable Octet.
The Stable Octet
o
o
Ions
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Factors That Determine
Chemical Reactivity
1. The number of electrons in the outer energy level.
Rules:
a.
b.
c.
2. The Atomic Radius (number of energy levels / shells)
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Ions Negatively Charged Ions = Anions
Positively Charged Ions = Cations
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Electron Dot Diagrams (EDD)
A Bohr – Rutherford diagram represents an atom and
all its electrons.
A simpler way to represent atoms and ions of atoms is
with electron dot diagrams.
Electron Dot Diagrams
o
Examples:
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Nomenclature: Binary Ionic, Polyatomic, and Multivalent
1. BONDING CAPACITY (VALENCE) The number of bonds an atom can make. For a Cation, the bonding capacity is the number of electrons lost to become stable. For an Anion, the bonding capacity is the number of electrons gained to fill the outer energy level to eight. Ex. For sodium the bonding capacity is one. For oxygen the bonding capacity is two. 2. OXIDATION NUMBERS The charge of the ion of an atom. Ex. For sodium the oxidation number is +1. For oxygen the oxidation number is -2. 3. NAMING ELEMENTS All elements (substances composed of only one type of atom) are named as on the periodic table. Ex. Mg Magnesium Fe Iron 4. NAMING BINARY IONIC COMPOUNDS Binary ionic compounds are compounds containing only two elements (a metal and a non-metal) RULES: 1. Write the cation (metal) first, using the name of the element as on
the periodic table. 2. Write the anion second, dropping the usual ending (-ine, -ium,
-ogen etc.) and replace it with -ide. Ex. NaCl sodium chloride KBr potassium bromide K2O potassium oxide
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chemical formula
chemical name
NaI
BeF2
MgO
Na2O
Li2S
BCl3
Al2O3
K2S
5. WRITING FORMULA FOR BINARY IONIC COMPOUNDS RULES: 1. Write the symbol for the cation (metal) then write the symbol for the
anion (nonmetal) beside. 2. Write the charge of the ion (oxidation number) for each element
above the element. 3. Use the zero sum rule to balance the charges of the ions. 4. Write the required number of atoms that satisfy the zero sum rule as
subscripts behind the ion to which it refers. Ex. # 1 potassium oxide Ex # 2 calcium nitride
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chemical name
chemical formula
sodium fluoride
lithium chloride
beryllium bromide
magnesium oxide
boron iodide
aluminum sulfide
potassium oxide
calcium fluoride
8. WRITING NAMES FOR POLYATOMIC IONS Polyatomic ions are groups of atoms which act as a unit. They consist of two or more different non-metal atoms joined by a covalent bond. The bonding capacity of the polyatomic ion is the same as the charge.
PO4-3 phosphate ClO3
-1 chlorate
SO4-2 sulfate NO3
-1 nitrate
CO3-2 carbonate OH-1
hydroxide
NH4+1 ammonium HCO3
-1 hydrogen carbonate
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RULES: 1. Write the cation first, using the name of the element as on the periodic table. 2. Write the name of the polyatomic ion with the -ate ending. Ex. Na2(SO4) sodium sulfate
9. WRITING FORMULA FOR POLYATOMIC IONS RULES: 1. Write the symbol for the cation or polyatomic ion named first then
write the symbol for the polyatomic ion or anion named second. 2. Write the charge of the ion (oxidation number) for each element
or polyatomic ion above each element or polyatomic ion. Put brackets around the polyatomic ion.
3. Use the zero sum rule to balance the charges of the ions. 4. Write the required number of atoms that satisfy the zero sum rule as
subscripts behind the ion to which it refers. Ex. # 1 Magnesium sulfate Ex # 2 ammonium chloride
chemical name
chemical formula
chemical formula
chemical name
ammonium sulfate
H3PO4
sodium hydroxide
K2CO3
magnesium sulfate
H2SO4
hydrogen carbonate (NH4)2S
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Nomenclature: Molecular compounds
1. NAMING DIATOMIC GASES The following gases exist in nature in a diatomic form having the general chemical formula "X2". The names of these binary compounds are found by just using the element's name from the Periodic Table.
Name of diatomic gas
Formula for diatomic gas
hydrogen
oxygen
nitrogen
fluorine
F2
chlorine
bromine
iodine
2. NAMING MONATOMIC GASES The elements of Group 8A (Noble gases) exist in nature as monatomic gases. These gases are considered "inert" or unreactive under most conditions. Some may react under extreme pressures or temperatures. These elements are not binary chemical compounds, but you should know the names and formulas of these elements. Use your Periodic Table to determine the noble gas that is at the end of each period.
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period
name of gas
formula or symbol
period 1
period 2
period 3
period 4
krypton
period 5
Xe
period 6
3. NAMING BINARY MOLECULAR (COVALENT) COMPOUNDS Binary molecular (covalent) compounds are compounds containing only two elements (a non-metal and a non-metal) RULES: 1. Attach a prefix that indicates the number of atoms in the chemical formula to the front the name of element that is more to the left on the periodic table. The prefix "mono-" is omitted from the name of the first element if it is the prefix required. The Greek prefixes are as follows. mono - 1 tetra - 4 hepta - 7 deca - 10 di - 2 penta - 5 octa - 8 tri - 3 hexa - 6 nona - 9 2. A second prefix indicating the number of atoms in the chemical formula is attached to the second name of the element. This element is usually found on the right of the periodic table. The name of the second element ends in -ide. 3. The "o" or "a" ending of the prefix is omitted if the cation or anion name starts with an "o" or "a". Ex. P2O3 is called diphosphorous trioxide
N2O5 is called dinitrogen pentoxide
CO2 is called carbon dioxide
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chemical formula
chemical name
CO2
As2O3
NO2
P2O5
CBr4
SF6
SeO2
4. WRITING FORMULA FOR MOLECULAR (COVALENT) COMPOUNDS RULES: 1. Write the elemental symbol for each of the elements named. 2. Use the prefixes to determine the number of elements in each molecule. Ex. dinitrogen tetroxide N2O4
carbon tetrachloride CCl4
diphosphorous trisulfide P2S3
sulfur hexafluoride SF6
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chemical name
chemical formula
nitrogen monoxide
sulfur trioxide
phosphorus pentabromide
dinitrogen trioxide
carbon tetrachloride
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Chemical Bonding
Most substances on earth do not exist as elements, they are
composed of 2 or more different elements joined together called
_______________ .
Compounds are formed from chemically bound atoms or ions.
Atoms tend to gain, lose, or share electrons until they have 8 valence
electrons ( _____________________ ).
When 2 atoms collide, valence electrons on each atom interact
(BONDING ONLY INVOLVES THE VALENCE ELECTRONS!). A
chemical bond forms between them if the new arrangement of their
valence electrons has less energy than their previous arrangement.
For many atoms, that new arrangement of their electrons will be that
of the nearest noble gas.
Atoms may acquire a valence shell like that of its closest noble
gas in one of three ways:
1.
2.
3.
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Ionic Compounds
Substances held together by ionic bonds are called
Ionic compounds. Ionic bonds form between metals and
non-metals.
e.g. NaCl, KCl.
Ionic Bonds occur because of the attraction of cations
and anion for each other. Ionic bonds are the electrostatic
attraction between opposite charges. Electrons are
transferred between the atoms during bond formation.
PROPERTIES INCLUDE:
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Ionic Compounds
We can show ionic bonding with Electron Dot Diagrams.
Na and Cl
K and O
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Molecular Compounds
Substances that are composed of molecules are called
Molecular compounds.
e.g. H2O, O2
Although covalent bonds
between atoms of a
molecule are strong,
bonds between more than one molecule are weak (eg. Moth
crystals, nitrogen gas).
PROPERTIES INCLUDE:
DIATOMIC MOLECULES
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Molecular Compounds
We can use Electron Dot Diagrams to show covalent bonds.
N 2
H2O
O 2
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Balanced and Unbalanced Chemical Equations
The Law of Conservation of Mass states:
Therefore, the number of atoms in the reactants must equal the number atoms in the products!
An unbalanced or skeleton equation does not follow the Law of
Conservation of Mass. The number of atoms on the left side
(reactants) does not equal the atoms on the right side (products).
e.g.
A balanced chemical equation follows the Law of Conservation of
Mass. The number of atoms on the left side (reactants) equals the
atoms on the right side (products).
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How to Write Balanced Chemical
Reactions
1. Write the chemical formula for each reactant and product
followed by the state of each:
2. Adjust the numbers of molecules using coefficients
( )
until there is the same number of atoms of each type on both sides of
the equation. This balances the mass of both the reactants and
products.
3. Usually, balancing is easiest when hydrogen and oxygen
atoms are left until the end.
NOTE: Do not change the subscript in a formula to balance an equation.
Changing these numbers changes the molecular structure of the
molecule.
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Chemical Equations and
Reactions
A chemical equation is a description of a
chemical reaction using chemical symbols, not
words! Steps:
1)
2)
3)
4)
e.g. Word Equation
Hydrogen gas plus chlorine gas produces hydrogen chloride gas
e.g. Chemical Equation H2 ( g ) + Cl2 ( g ) HCl ( g )
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Types of Chemical Reactions SYNTHESIS
Involves the combination of smaller atoms and
/or molecules into larger molecules
Two or more reactants combine to make one
product
DECOMPOSITION Opposite to synthesis
Involves the splitting of a large molecule into elements or smaller molecules
One reactant breaks apart into two or more products
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SINGLE DISPLACEMENT
Involves one element replacing or displacing a second
element in a compound
A metal element will only displace a metal in a compound.
e.g.
A non-metal will only displace a non-metal in a compound.
e.g.
DOUBLE DISPLACEMENT
Involves both elements in different compounds displacing each
other or exchanging places.
The metals switch places and the non-metals switch places
o Analogy - two couples dancing and they switch partners
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ACIDS AND BASES
Acids and Bases Acids are solutions that contain a large amount of H+ ions
Bases are solutions that contain a large amount of OH- ions
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Properties of Acids and Bases
Property Acids Bases
Taste
Touch
Indicator Tests
Reaction with metals
Type of oxide reacting with water
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RATES OF REACTIONS
The rate of a reaction is the amount of ______________ produced during a given time.
The __________________________ states that the rate of reaction is affected by the
number of reactant molecules. Molecules in a
or a ________________ are constantly colliding with each other.
Factor Affecting the Rate of Reaction
Molecules during a slow rate of reaction
Molecules during a fast rate of reaction
Temperature
Concentration
Surface Area
Catalyst
Provide an example for each factor that changes the rate of reaction
a) Temperature: __________________________________
b) Concentration: _________________________________
c) Surface Area: __________________________________
d) Catalyst: ______________________________________
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pH Indicators
Indicators:
Examples: 1. Litmus paper
2. Phenolphthalein
Indicators can be made from flowers, fruits,
vegetables, leaves (eg. Red cabbage).
Synthetic indicators are easier to use than natural
indicators because they:
1 .
2 .
Examples of synthetic indicators:
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Neutralization
Neutralization occurs when hydroxide ions (base) and
hydrogen ions (acid) are mixed to make water. The general
word equation is:
After neutralization, the solution no longer has a high
concentration of either ion.
Careful inspection of the beakers will reveal that the ions that have
undergone reaction are the H+ and OH- ions. The Na+ ions and Cl-
ions remain unchanged before and after the reaction. The Na+ ions
and the Cl- ions are called spectator ions.
Before Neutralization:
After Neutralization:
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If we leave out the spectator ions, and write the equation
involving those ions that participated in the reaction, we write the
net ionic equation of neutralization.
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The pH Scale! Definition of pH:
The change in 1 pH unit represents a 10-fold increase (or decrease) in the concentration of hydrogen ions in solution. A pH of 2 is 10x stronger than a pH of 3 A pH of 2 is _____ stronger than a pH of 5 A pH of 2 is _____ stronger than a pH of 7
The scale is numbered from 0 to 14:
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The Strength of Acids and Bases The strength of an acid or base depends on 2 factors:
1 .
2.
THE pH OF ACIDS – strength of acids The number of ___________ produced when an acid is mixed
with water will determine the strength of the acid.
Strong Acid Weak Acid
THE pH OF BASES – strength of bases The number of ____________ produced when a base is mixed
with water will determine the strength of the base.
Strong Base Weak Base
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Acids and Bases Problems 1. Strength of acids and bases on the pH scale. a) Base #1 has a pH of 9. Base #2 has a pH of 13. Which is more basic? How many more times basic is your choice? b) Lemon juice has a pH of 2. Vinegar has a pH of 5. Which is more acidic? How many times more acidic is your choice? 2. What are the products of the following reactions? Write balanced chemical equations for each reaction. a) nitrogen dioxide plus water produces ? b) lithium oxide plus water produces ? c) magnesium oxide plus water produces ? d) carbon dioxide plus water produces? 3. Neutralization of acids and bases. Identify the salt produced in each of the following neutralization reactions and balance the reaction. a) HCl (aq) + Ca(OH)2 (aq) b) H2SO4 (aq) + LiOH (aq) c) H2CO3 (aq) + KOH (aq) d) H3PO4 (aq) + Ba(OH)2 (aq) e) HNO3 (aq) + NaOH (aq)
4. You are required to make the salt Ca(SO4) in the lab, but are given only the following chemicals:
BaO CaO SO4 CO3 SO3 LiO2 K2O H2O SO2 CO2
Use balanced chemical reactions to make the necessary acid and the base. You will then use a balanced chemical reaction to show how your acid and base can be used to make Ca(SO4).