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Chemical Symbols, Formulas & Equations
Chemical SymbolsA symbol represents
one element (1-3 letters)
Symbol Writing Rules1st letter is always
capitalized2nd & 3rd letters (if
any) are always lower case
Symbols
OOxygen
SnTin
UutUnuntriu
m
CoCobalt
element #27bluish metal
COCarbon monoxide
Molecule:( 1 carbon, 1 oxygen)colorless, odorless,
tasteless, deadly gas
Co v CO
IUPAC Naming New ElementsNew elements are being synthesized (made) in the labNames for the element has to wait until the IUPAC naming
committee meetsA temporary name based on the atomic number IN LATIN is
given to the new elementTime to learn some Latin
Rules for naming elements1. Break up the atomic number into digits (#118 becomes 1, 1, 8)2. Replace the digits with the Latin number (1, 1, 8 becomes un un
oct3. Put the Latin numbers together and add “–ium” ending –
ununoctium4. The symbol is the first letter of each of the Latin numbers (follow
the rules) ununoctium - Uuo
• 1 – un• 2 – bi• 3 – tri
• 4 – quad • 5 – pent• 6 – hex
• 7 – sept 0-nil• 8 – oct• 9 – enn
IUPAC SamplesAtomic Number Symbol
113 UutName
ununtrium
234 Btqbitriquadium
506 Pnhpentnilhexium
Chemical FormulasChemical “shorthand” to describe a compoundGives the symbol & number of atoms of each
elementRules for Formulas
1. every Capital letter indicates another element2. a lowered number (called a subscript) after an
element tells you how many atoms of that element are in the compound/molecule (no subscript means 1)
3. A number in front of a FORMULA tells you how many units or molecules of that substance there are (this is called the formula coefficient)
Examples (Formula Rules 1 & 2)
Compound Formula # Atoms of Each Element
Carbon Dioxide CO2 1 -Carbon 2- Oxygens
Sugar C6H12O6 6-Carbons 12 - Hydrogens 6-Oxygens
Copper Sulfate CuSO4 1-Copper 1-Sulfur 4-Oxygens
Baking Soda NaHCO3 1-Sodium 1-Hydrogen 1-Carbon 3-Oxygens
Polyatomic Ions (parts in parentheses)Some combinations of elements bond together and
act like an element – they usually stay togetherExamples:
Phosphate PO4
Hydroxide OHAmmonium NH4
Acetate C2H3O2
Nitrate NO3
Because there is more than one element bonded together, if more than one polyatomic ion is needed youWrap parentheses around the ion in the formulaPut the subscript outside the parentheses
Counting Elements with ()Since the polyatomic ion acts like an
element, its subscript multiplies the number of ions needed
Ex. ClO3 is a poly atomic ion called chlorate so…
Mg(ClO3)2 means we have 1 magnesium and 2 chloratesBut each chlorate is 1-chlorine and 3-oxygensTherefore the subscript outside the ()
multiplies the each of the number of elements inside the parentheses for the total
(ClO3)2 ends up with 2-chlorines (2 *1) and 6-oxygens (2*3)
Counting with Polyatomic Ions Samples
Formula Element Count
Ca3(PO4)2
Al(C2H3O2)3
3-Calcium2-Phosphorous
(2*1)8-Oxygen (2*4)
1-Aluminum6-Carbon (3*2)9-Hydrogen (3*3)6-Oxygen (3*2)
Al
Review Practice
Compound Contents
HgBr2
Be(NO3)2
Al(C2H3O2)3
1-Mercury2-Bromine
1-Beryllium2-Nitrogen (1*2)6-Oxygen (3*2)
1-Aluminum6 Carbon (2*3)9-Hydrogen (3*3)6-Oxygen (2*3)
Example (Formula Rule #3)
C2H6O + 3O2 3H2O + 2CO21- C2H6O molecule is needed (no number means 1)
3- O2 molecules are needed
3- H2O molecules are needed
2- CO2 molecules are needed
2-Carbons6-Hydrogens1-Oxygen
6-Oxygens6-Hydrogens3-Oxygens
2 Carbons4-Oxygens
Coefficient Samples
Formula Contents
4 H2O
2 MgCl2
3 C6H12O6
4*2 = 8 Hydrogen4*1 = 4 Oxygen
2*1 = 2 Magnesium2*2 = 4 Chlorine
3*6 = 18 Carbon3*12 = 36 Hydrogen3*6 = 18 Oxygen
Do # 18, 19, 20 on back page
Review Video
Putting it all togetherSince a coefficient multiplies the number of
compounds thenThe coefficient will also multiply the number
of polyatomic ionsRule: The coefficient AND a subscript
outside the parentheses BOTH multiply the elements inside the parentheses.
Example 3 Ca3(PO4)2
9-Calcium (3*3)6-Phosphorus (3*1*2)24-Oxygen *(3*4*2)
Other Examples
Compound Count
3 (NH4)2SO4
4 Cu(NO3)2
6-Nitrogen (3*1*2)24-Hydrogen
(3*4*2)3-Sulfur (3*1)12-Oxygen (3*4)
4-Copper (4*1)8-Nitrogen (4*1*2)24-Oxygen (4*3*2)
Conservation of MassMatter cannot be created or destroyed (actually
the law states that the total amount of matter + energy in a closed system remains constant but that is a little lofty for what we will be doing)
For Us: In a reaction the total number of elements we start the reaction with must equal the total number of elements we end with.
Example H2 + O2 H2O
Since the totals on each side of the are not equal we need to use coefficients to “balance” the equation
Balancing a Chemical Equation
Samples Samples
S + O2 SO2
1- sulfur2-oxygen
1-sulfur2-oxygen
1-sodium2-oxygen
2-sodium1-oxygen
Na + O2 Na2O
x2
1-sodium2-oxygen
4-sodium2-oxygen
x4
4-sodium2-oxygen
4-sodium2-oxygen
4 Na + O2 2Na2O
Na + O2 2 Na2O
H2 + Cl2 HCl2- hydrogen
2-chlorine1-hydrogen1-chlorine
H2 + Cl2 2HCl
2-silver1-oxygen
1-silver2-oxygen
x2
4-silver2-oxygen
1-silver2-oxygen
2 Ag2O Ag + O2
x2
2- hydrogen2-chlorine
2-hydrogen2-chlorine
Ag2O Ag + O2
2 Ag2O 4Ag + O2
x4
Balancing a Chemical Equation
Equation Procedure
H2 + O2 H2O
Count the atoms on each side of the equation ()2-hydrogen
2-oxygen2-hydrogen1-oxygen
need to multiply the oxygen on the right by 2
2-hydrogen2-oxygen
4-hydrogen2-oxygen
4-hydrogen2-oxygen
4-hydrogen2-oxygen
x2
x2
2H2 + O2 2H2O
H2 + O2 2H2O
Select one of the elements that are out of balance and use a coefficient to multiply its compound & recount
Repeat this process until all elements are balanced (numbers of an element are the same on each side)
Change ONLY the COEFFICIENTS, NEVER the SUBSCRIPTS!!
1- carbon4-hydrogen2-oxygen
1- carbon2-hydrogen3-oxygen
Balancing a Chemical Equation
Samples Samples
CO + O2 CO2
1- carbon3-oxygen (1/2)
1-carbon2-oxygen
2-nitrogen2-hydrogen
1-nitrogen3-hydrogen
N2 + H2 NH3
x2
2-nitrogen6-hydrogen
2-nitrogen6-hydrogen
2 CO + O2 2CO2
N2 + 3H2 2NH3
CH4 + O2 CO2 + H2O1- carbon4-hydrogen2-oxygen
CH4 + O2 CO2 + 2H2O
x2 CH4 + 2O2 CO2 + 2H2O
x2x2x2 just the CO
x3
2-carbon4-oxygen (1/2)
2-carbon4-oxygen
1- carbon4-hydrogen4-oxygen
1- carbon4-hydrogen4-oxygen
1- carbon4-hydrogen4-oxygen
2- hydrogen2-nitrogen1-oxygen
Balancing a Chemical EquationSamples
H2 + NO H2O + N22- hydrogen1-nitrogen1-oxygen
H2 + 2NO H2O + N2
x2
H2 + 2NO 2H2O + N2
x2
x2
2- hydrogen2-nitrogen2-oxygen
2- hydrogen2-nitrogen1-oxygen2-
hydrogen2-nitrogen2-oxygen
4- hydrogen2-nitrogen2-oxygen
2H2 + 2NO 2H2O + N2
2- hydrogen2-nitrogen2-oxygen
4- hydrogen2-nitrogen2-oxygen
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