Transcript COUNTING ATOMS - Ms. Wasson's Class

Bellwork
• Pick up a yellow Chemical Equations notes
sheet and glue it into your comp book.
• Pick up a pink sheet to SHARE with you and
your shoulder partner.
• Follow the directions on the Pink sheet to
review what we learned on Tuesday about
bonding. Complete this entire sheet with your
partner, taking turns writing and looking up –
you must work EQUALLY!
BONDING REVIEW &
PRACTICE
Ionic Bonds
• Ionic bonds exist between a non-metal
and a metal
• When two atoms bond ionically, they
gain/lose electrons
• When an atom gains or loses an electron,
it becomes an ion (an atom with a
positive or negative electrical charge)
Ions
Group
1
18
2
13 14 15 16 17
3
4
5
6
7
8
9
10 11 12
Cation
Positive ion
(a metal gives away
electrons in ionic
bonding and becomes
positively charged)
Anion
Negative ion
(a nonmetal takes
electrons in ionic
bonding and becomes
negatively charged)
Covalent Bonds
• Covalent bonds exist between NONMETAL
and NONMETAL.
– Example: H2, H2O, NO3, CH4
• Covalent bonds SHARE electrons.
• Shared electrons don’t belong to either atom.
To Do
• Complete the “Bonding Basics” practice in your packet.
1. Draw the bonds, as specified
2. Write the chemical formula for each compound
3. Number 3 under Covalent Bonds is Optional. You can do
the simpler bond of Hydrogen and Oxygen instead, or you
can try the challenge.
4. Extra Challenge: Follow the instructions in your packet
to try and write the correct names for each compound.
Chemical Equation
The symbolic representation of a chemical
reaction.
Reactants
Coefficient:
Tells the amount of
that compound in
the equation.
Multiply it through
the whole
compound.
yield
Products
Subscript:
Tells the amount of
the element that
comes before it.
1) Combustion: A combustion reaction is when oxygen combines with another compound to form water and
carbon dioxide. These reactions are exothermic, meaning they produce heat. An example of this kind of
reaction is the burning of napthalene:
C10H8 + 12 O2 ---> 10 CO2 + 4 H2O
2) Synthesis: A synthesis reaction is when two or more simple compounds combine to form a more
complicated one. These reactions come in the general form of:
A + B ---> AB
One example of a synthesis reaction is the combination of iron and sulfur to form iron (II) sulfide:
8 Fe + S8 ---> 8 FeS
3) Decomposition: A decomposition reaction is the opposite of a synthesis reaction - a complex molecule
breaks down to make simpler ones. These reactions come in the general form:
AB ---> A + B
One example of a decomposition reaction is the electrolysis of water to make oxygen and hydrogen gas:
2 H2O ---> 2 H2 + O2
4) Single displacement: This is when one element trades places with another element in a compound. These
reactions come in the general form of:
A + BC ---> AC + B
One example of a single displacement reaction is when magnesium replaces hydrogen in water to make
magnesium hydroxide and hydrogen gas:
Mg + 2 H2O ---> Mg(OH)2 + H2
5) Double displacement: This is when the anions and cations of two different molecules switch places,
forming two entirely different compounds. These reactions are in the general form:
AB + CD ---> AD
+ CB
One example of a double displacement reaction is the reaction of lead (II) nitrate with potassium iodide to
form lead (II) iodide and potassium nitrate:
Pb(NO3)2 + 2 KI ---> PbI2 + 2 KNO3
6) Acid-base: This is a special kind of double displacement reaction that takes place when an acid and base
react with each other. The H+ ion in the acid reacts with theOH- ion in the base, causing the formation of
water. Generally, the product of this reaction is some ionic salt and water:
HA + BOH ---> H2O + BA
One example of an acid-base reaction is the reaction of hydrobromic acid (HBr) with sodium hydroxide:
HBr + NaOH ---> NaBr + H2O
Reactants
yield
Products
Balanced or Not?
Does it follow the Law of Conservation
of Mass/Matter?
Count the atoms on both sides!
Fill in your packet for the Law!
COUNTING
ATOMS
Make an Inference
How many atoms of each element are in this
formula:
2H2O
RULES FOR COUNTING
ATOMS
1. SUBSCRIPTS only refer to the
atom that they are BEHIND. For
example…
H2S
There are TWO atoms of
HYDROGEN and only ONE atom
of SULFUR.
COEFFICIENTS
2. COEFFICIENTS apply to the entire
compound. You MULTIPLY the
coefficients and SUBSCRIPTS.
2 H2S
ATOMS OF HYDROGEN: 4
ATOMS OF SULFUR: 2
IF THERE ISN’T A SUBSCRIPT BEHIND AN
ELEMENT, ASSUME THERE IS ONLY ONE ATOM OF
THAT ELEMENT!
PARENTHESES
3. If elements or compounds are inside of
PARENTHESES, then the SUBSCRIPT
behind the parentheses applies to
everything inside.
Ba(OH)2
ATOMS OF BARIUM:
1
ATOMS OF OXYGEN:
2
ATOMS OF HYDROGEN: 2
LET’S PRACTICE!
MgCl2
Atoms of Magnesium: 1
Atoms of Chlorine: 2
Al2S3
Atoms of Aluminum: 2
Atoms of Sulfur: 3
PRACTICE
H2SO4
Atoms of Hydrogen: 2
Atoms of Sulfur: 1
Atoms of Oxygen: 4
CH3OH
Atoms of Carbon: 1
Atoms of Hydrogen: 4
Atoms of Oxygen: 1
THIS COULD BE A LITTLE
TRICKY…
Ca3(PO4)2
Atoms of Calcium: 3
Atoms of Phosphorus: 2
Atoms of Oxygen: 8
Al2(SO4)3
Atoms of Aluminum: 2
Atoms of Sulfur: 3
Atoms of Oxygen: 12
What about this BAD BOY???
2Ca3(PO4)2
Atoms of Calcium: 6
Atoms of Phosphorus: 4
Atoms of Oxygen: 16