Chemical Bonds and Chemical Bonds and Balancing EquationsBalancing Equations

EQ: Why do chemicals react? EQ: Why do chemicals react? What is the difference between What is the difference between

compounds, mixtures, and solutions?compounds, mixtures, and solutions?

Important TermsImportant Terms

Molecule- is two or more atoms combined Molecule- is two or more atoms combined and are physically attached and are physically attached

Compound- is when two or more elements Compound- is when two or more elements are combined by chemical bonds (NaCl, are combined by chemical bonds (NaCl, Sugar..ect) and is a solidSugar..ect) and is a solid

Solution- is when two or more elements Solution- is when two or more elements are combined by chemical bonds and are are combined by chemical bonds and are in a liquid state. (every drop is the same in a liquid state. (every drop is the same concentration HCL, Vinegar) concentration HCL, Vinegar)

Important TermsImportant Terms

Mixture- is when two or more elements are Mixture- is when two or more elements are combined but ARE NOT chemically combined but ARE NOT chemically bonded (liquid or solid)bonded (liquid or solid)

Heterogeneous mixture- Not an even mix Heterogeneous mixture- Not an even mix throughout, (chocolate milk, salt and throughout, (chocolate milk, salt and pepper, Italian salad dressing)pepper, Italian salad dressing)

Homogeneous mixture- Even mix Homogeneous mixture- Even mix throughout (milk, sand, and smoke)throughout (milk, sand, and smoke)

RecallRecall

Why do elements react?Why do elements react?To achieve a more stable electron To achieve a more stable electron

configuration (full outer shell)configuration (full outer shell)

What types of bonds are What types of bonds are created?created?

Ionic-electrons are transferred from one Ionic-electrons are transferred from one element and give to another: element and give to another: STRONGEST CHEMICAL BONDSTRONGEST CHEMICAL BOND

New termsNew termsCation-positive element Cation-positive element Anion-negative elementAnion-negative elementSo sodium is a cation and chloride is the So sodium is a cation and chloride is the

anion in NaCl(salt)anion in NaCl(salt)

Covalent bondCovalent bond

Atoms share electrons: NO ELECTRONS Atoms share electrons: NO ELECTRONS ARE SHIFTED OR REMOVEDARE SHIFTED OR REMOVED

Can create either single or double bonds Can create either single or double bonds to achieve full outer shellto achieve full outer shell

Most Commonly done with gases that do Most Commonly done with gases that do not have a full outer shell (Onot have a full outer shell (O2 2 Cl Cl2 2 N N2 2 ))

Atoms of the gases join up to achieve Atoms of the gases join up to achieve stability (weak bond, easily broken) stability (weak bond, easily broken)

Understanding Chemical Understanding Chemical reactionsreactions

Look at the following equation:Look at the following equation:The reactants are to the left of the arrowThe reactants are to the left of the arrowThe products are to the right of the arrowThe products are to the right of the arrow ReactantsReactants ProductsProductsAg(NOAg(NO33) + NaCl -------) + NaCl ------- AgCl + Na(NO AgCl + Na(NO33))

Now list elements in both the Now list elements in both the reactants and productsreactants and products

MAKE SURE ALL ARE LISTEDMAKE SURE ALL ARE LISTED

ReactantsReactants ProductsProductsAgAg AgAgNN NNOO OONaNa NaNaClCl ClCl

Now write the number of atoms Now write the number of atoms of each elementof each element

REACTANTSREACTANTS PRODUCTSPRODUCTS 1 Ag1 Ag 1 Ag 1 Ag 1 N 1 N 1 N 1 N 3 O 3 O3 O 3 O 1 Na 1 Na1 Na 1 Na 1 Cl 1 Cl1 Cl 1 Cl

Notice that ALL The atoms listed are Notice that ALL The atoms listed are EQUAL in number on BOTH SIDES of the EQUAL in number on BOTH SIDES of the reaction reaction

In a chemical formula you assume the In a chemical formula you assume the number 1 when no other number is listednumber 1 when no other number is listed

Notice that oxygen has 3 as its number! Notice that oxygen has 3 as its number! This is because oxygen is part of a This is because oxygen is part of a polyatomic molecule. There are 3 oxygen polyatomic molecule. There are 3 oxygen atoms joined with the formulaatoms joined with the formula

Now consider this formulaNow consider this formula

CHCH44 + O + O22 ----------------> CO ----------------> CO22 + H + H22OO ReactantsReactants ProductsProducts CC CC HH HH OO OO

How many atoms are listed for How many atoms are listed for the products and reactantsthe products and reactants

ReactantsReactants ProductsProducts 1 C1 C

1C1C 4 H4 H 2 2

HH 2 O2 O 3 3

OO THIS CAN NOT HAPPEN! You must Balance the THIS CAN NOT HAPPEN! You must Balance the

equation so that numbers of atoms for the reactants equation so that numbers of atoms for the reactants

equal the same number for the Productsequal the same number for the Products

To do this we place numbers in front of To do this we place numbers in front of the molecules in the formula to balance the molecules in the formula to balance the atoms outthe atoms out

CHCH44 + O + O22 ----------------> CO ----------------> CO22 + H + H22OO (Start with the atom with the highest (Start with the atom with the highest

number for either reactants or products) number for either reactants or products) It would be H in the exampleIt would be H in the example

ReactantsReactants ProductsProducts 1 C1 C 1C1C 4 H4 H 2 H2 H 2 O2 O 3 O3 O We need 2 more H in the products so we place a 2 in front of We need 2 more H in the products so we place a 2 in front of

the water moleculethe water molecule CHCH44 + O + O22 ----------------> CO ----------------> CO22 + 2 H + 2 H22OO

Now RecheckNow Recheck

ReactantsReactants ProductsProducts 1 C1 C 1C1C 4 H4 H 4 H4 H 2 O2 O 4 4

OO Now we need to balance out the Oxygen in the Now we need to balance out the Oxygen in the

Reactants.Reactants. CHCH44 + 2 O + 2 O22 ----------------> CO ----------------> CO22 + 2 H + 2 H22OO

RecheckRecheck

ReactantsReactants ProductsProducts 1 C1 C

1C1C 4 H4 H 4 4

HH 4 O4 O 4 4

OO It is now balanced!!!It is now balanced!!!

HomeworkHomework

Balance this equation (its harder than it Balance this equation (its harder than it looks)looks)

Al + OAl + O22 -----------> Al -----------> Al22OO33