Chemical Symbols - Each element has a one, two or three letter symbol to represent it - Symbols with more than one letter are always written capital letter then lower case letter Diatomic molecules - elements found only combined covalently in nature H 2 , N 2 , O 2 , F 2 , Cl 2 , Br 2 , I 2 - Based on IUPAC system of naming
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Chemical Symbols- Each element has a one, two or three letter symbol to represent it - Symbols with more than one letter are always written capital letter.
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Chemical Symbols - Each element has a one, two or three letter symbol to represent it
- Symbols with more than one letter are always written capital letter then lower case letter
Diatomic molecules - elements found only combined covalently in nature
H2, N2, O2, F2, Cl2, Br2, I2
- Based on IUPAC system of naming
Element vs. Compound
Element
Cannot be chemically broken down into two different substances.
- Atoms of all the same type
Compound Combination of elements
a. All sample of a compound have the same properties
c. All areas of a compound are the same
Na Cu
NaCl CuSO4
b. Atoms in a compound are in a simple ratio
What’s in a Quarter?
What two elements do you think are found in a quarter? (Write the name an symbol below.
What do you think will happen when the RED HOT quarter is placed into the beaker of methanol?
Describe what did happen?
Is the reaction that took place exo or endothermic/
Why did the quarter change color?
Chemical formulas tell us two thingsType of elements present
Number of atoms
Examples
MgBr2
Al2O3
Ca(OH)2
1 Mg for every 2 bromines
2 aluminums for every 3 oxygens
1 calcium , 2 hydrogens and 2 oxygens
2 sets of OH
Example - How many sulfur atoms are present in Pb(SO4)2?2
How many oxygen atoms are present? 4 x 2 = 8
Subscript- Indicates number of atoms
Coefficients -numbers placed in front of a chemical formula to indicate how many molecules are present
2. Ternary compounds Compounds with 3 or more elements
-usually a metal with a POLYATOMIC ION
Polyatomic ion Group of atoms bonded together to obtainan overall charge
Has special properties unlike the individual atoms
Often acts as one atom
Found on Table E
O |O - P - O | O
-3
PO4-3 phosphate
Name the following polyatomic ionsSO3
-2 OH- CO3-2 NH4
+
sulfite hydroxide carbonate ammonium
Polyatomic ions bond IONICALLY with other ions
Naming compounds with polyatomic ions
- Do not change any parts, take the name of each part of the compound
-Circle the polyatomic ion in each compound, then name the compound
MgSO4 NaSCN
LiOH NH4OH
CaCO3 Li2SO3
Al(OH)3
Magnesium sulfate
Lithium hydroxide
Calcium carbonate
Aluminum hydroxide
Sodium thiocyanate
Ammonium hydroxide
Lithium sulfite
Naming Covalent Compounds
-compounds with only nonmetals
-using Table S, write the name of the element with the lower electronegativity first
-use prefixes to tell how many of each element are present
Ex. CO2
2.6 3.4
Carbon dioxide
N2Cl2
3.0 3.2
Dinitrogen dichloride
2 oxygen's
Try: Carbon tetrachloride
Diphosphorous pentoxide
Name the following Compounds
LiBr
MgSO4
CaCO3
SrCrO4
ZnS
Al2(SO4)3
NH4NO3
Write the empirical formula
C2H2 PbCl4 H2O2C6H12O6 P2O4
Write out the following formulasCalcium oxide
Lithium Sulfide
Lithium Sulfate
Magnesium phosphate
Aluminum carbonate
Nitrogen dioxide
So far, we have learned how to take different elements and combine them together to make a compound.But there are some elements that have several oxidation states.
For example, what is the formula for lead oxide?Pb has two oxidation states Pb+2 and Pb +4
Pb+2 O-2
PbOPb+4 O-2
O-2
PbO2Which of the two is correct?
BOTH are correct!
How can we have two different formulas with the same name?We need a way to distinguish between these two.
- used when the first part of a compound (the positive one) has two or more positive oxidation states.
Which of the following requires the stock system?
CuO MgO LiNO3
NO CaSO4 Ni(NO3)2 ZnCO3
Yes NO
Yes YesNO
NO
NO
How is the stock system used?How is the stock system used?
1. Assign oxidation numbers to the elements in the compound
Pb+2 O-2
PbO
Pb+4 O-2
O-2
PbO2Pb is in the +2 state, so it is called
Lead (II) oxidePb is in the +4; state, so it is called
Lead (IV) oxide
SnCl2
The Cl must be in the -1 state, since Sn must be a positive oxidation state,
-1
Since there are two Cl’s, the Sn must be in the +2 oxidation state to cancel out the Cl’s
-2
+2Sn has an oxidation state of +2 or +4.
TinTin (II)(II) ChlorideChloride
+2 = 0
2. Write the oxidation state of first element as a roman numeral
Practice - All of the following compounds need the stock system. Determine the oxidation state of the cation (the first ion) and write out the name.
CuNO3
NiF2
HgO
Hg2O
FeCl3
NO2
-1+1Copper (I) nitrate
-1+2 Nickel (II) fluoride
-2+2-2+2
Mercury (II) oxide
-2+1 Mercury (I) oxide
-2+2
-1
-3
+3
+3
Iron (III) chloride
-2
-4
+4
+4Nitrogen (IV) oxide
If we are given a chemical name that uses the stock system, how do we write the formula?
Example - What is the chemical formula for Copper (II) oxide?
We know that the compound contains copper and oxygen
Cu O
And we know that oxygen must take a -2 oxidation state
-2
Don’t have to look up copper. The (II) tells us that it is in the +2 state
+2
What is the chemical formula for copper (II) oxide?
CuO
What is the formula for Nickel (III) sulfate?
Ni SO4
-2 According to chart E!+3
Ni2(SO4)3
Now write out the formulas for the following.
Nitrogen (II) chloride
Iron (III) oxide
Lead (IV) carbonate
Copper (I) sulfate
N+2 Cl-1 NCl2
Fe+3 O-2 Fe2O3
Pb+4 CO3-2 Pb(CO3)2
Cu+1 SO4-2 Cu2SO4
- Shows what happens during a chemical reaction
The chemicals involved
How many of each molecule
Energy used, phases
Reactants Substances that exist before the reaction takes place
Always found on the left, or facing away from the arrow
Products Substances that exist after a chemical reaction Always found on the right, or facing the arrow head
The reaction arrow is the “ “. It is always found in the middle of a chemical reaction and it divides up the reactants and the products
Examples - List the reactant and the products of the following reactions
a. 2 H2 + O2 2 H2O
b. HCl + NaOH H2O + NaCl
Reactants Products
2 H2 O2 2 H2O
HCl NaOH H2O NaCl
Balancing a chemical equation
How many carbon atoms are on each side of the equation?1
How many oxygens are on each side of the equation?Three on the reactants, but only 2 one the products side
Is this possible?No, something must happen to the other oxygenC=O O = OO
OOOO = ?
CO + O2 CO2
We need another CO for the other oxygen to attach to.
C=O O = OOOOO
O =
C=O
OO
OO
O =
So two molecules of CO combine with one molecule of O2
2 CO + O2 2 CO2
Now the equation is balanced because we have the same number and types of atoms on both sides
2 C 2 C4 O 4 O
Problem 1: Write the balanced equation for the reaction between aluminum sulfate and calcium chloride to produce aluminum chloride and a white precipitate of calcium sulfate.
Step 1: Write the word equationAluminum sulfate + Calcium chloride Aluminum chloride + Calcium Sulfate
Step 2: Replace the words with the correct formulas
Al2(SO4)3 CaCl2 AlCl3 CaSO4 + +
Step 3: Adjust coefficients to make the equation balance. Use trial and error until both sides have same number of each element.
Al2(SO4)3 + CaCl2 AlCl3 + CaSO4
This is a hit and miss procedure. Often you will need to change the coefficients several times in order to balance the equation correctly
Remember to only change the coefficients, not the molecular formula
Examples
a. ____ NH3 _____ N2 + ____ H2
b. ____ Li2SO4 + ____ Na ____ Na2SO4 + ____ Li
c. ____ HCl + ____ Mg ____MgCl2 + _____ H2
2
2 2
2
3
-Some pure elements must exist as DIATOMIC molecules
H Pure hydrogen gas is H2
N Pure nitrogen is N2
This occurs for the following elements
H, N, O, F, Cl, Br, I
Example - Balance the following equation
Nitrogen + oxygen nitrogen (II) oxide
N2 + O2 NO2
Showing Energy changes in Reactions
A. Reactions that require energy are endothermic
Ex. 2 H2O + energy 2 H2 + O2
B. Reactions that give off energy are exothermic
Ex. 2 H2 + O2 2 H2O + energy
Match-Making
The first matches were invented in 1827 by chemist John Walker. He determined that a wood splint tipped with antimony (II) sulfide, potassium chlorate, gum and starch could be ignited by striking it against a rough surface.
Write the formulas for the following compounds
Antimony (II) sulfide
Potassium chlorate
Describe the reaction that took place when Mr. Stone lite the mixture on fire.
Was the reaction exo or endothermic and explain why.Why safety matches?Combustible materials are