Download Why Bond? - Manasquan Public Schools

Compounds and
Molecules
4.1
vid
What are compounds?

Two or more elements
chemically combined to
form new substances.
What are compounds?
Chemical Bonds
– the attractive forces that hold
different atoms or ions
together


Bonds distinguish compounds
from mixtures.
Chemical Formula

C12H22O11 can only be sugar

H20 can only be water
Parts to the Formulas
2H2O
Coefficient
Subscript
Parts to the Formulas
Coefficient – gives the
amount of molecules or
moles
 Subscript – tells the
number of atoms or ions

Chemical Structure
 Bond length
-the distance between two
bonded atoms
 Bond angle
-the angle formed between
two bonded atoms
Models of compounds
Ball and stick model
-atoms are represented balls,
bonds are represented by sticks.

H
Bond length
Bond Angle
O
H
Models of compounds
Structural formulas
-chemical symbols represent
the atoms.

H
H
O
Models of compounds
Space-filling
-show the space occupied by
each atom represented in the
Hydrogen
compound.

Oxygen
Structure of Compounds

Network Structures = strong solids

Molecules= weak solids, liquids, or gases
Ionic and Covalent
Bonding
4.2
fun
Why Bond?
Atoms bond so they can
become stable!
 They want to achieve a
full outer energy level
 They want 8 electrons.

1. Ionic bond
A bond formed by the attraction
between oppositely charge ions.
 The joining of a positive metal
ion and a negative nonmetal ion

+
Na
+
Cl
NaCl
Ionic bond
Formed by transferring electrons
 Now each ion will have 8 valence
electrons

+
Na
+
Cl
NaCl
Ionic bond Properties
They form network structures
 high melting points
 Good conductors of electricity
when dissolved or melted
because of their ions

Metallic bond

Formed by the attraction
between positively charged
metal ions and the electrons
around them.
Metallic bond
Held together by free
flowing electrons
 Hold metallic elements
together

Covalent Bonds
Formed when atoms share
one or more valence
electrons
 Formed between non-metals
 May form single, double, or
triple bonds

Covalent Properties
They are poor conductors
of electricity (no ions)
 Low melting points.
 form molecules

Polyatomic ion
An ion made of two or more atoms
that are covalently bonded and that
act like a single ion.
 A molecule with a charge
-2
 Examples: carbonate (CO3)
Nitrate (NO3)-1


Fun
Compound Names
and Formulas
4.3
REMEMBER!!!!!!!!




If it starts with metal it is an ionic
compound
If it starts with a nonmetal it is a
covalent compound
If the formula contains a parentheses
(polyatomic ion) it contains both ionic
and covalent bonds
If it is just a metal it is metallic
Writing Ionic Formulas
Calcium Fluoride
Step 1 Look up both positive and
negative ions
2+
Ca
-1
F
Writing Ionic Compounds
Step 2
Criss-cross numbers down, making
subscripts
2+
Ca
-1
F
Ca1
F2
Writing Ionic Compounds
Step 3
Combine your new compound.
Ca1 + F2 
Ca1F2
Polyatomic ion
Aluminum Carbonate
+3
 Al


Al2
-2
)
(CO3
(CO3)3
Al2(CO3)3
Naming Ionic Compounds

Step one – Name the first
ion in the formula
Ex. CaCl2 – calcium
Na2(SO4) - sodium
Naming Ionic Compounds

Step two – Name the
second ion
Ex. CaCl2 –Calcium Chloride
Na2(SO4)-sodium sulfate
PROBLEM
Ex. Fe2O3 and FeO are different
compounds from different ions

Fe3+ O2- = Fe2O3
2+
 Fe
2O
= FeO
Solution-Roman Numerals
Same naming scheme
 Add a Roman Numeral to
identify the charge of the
metal ion.

Solution-Roman Numerals
Fe2O3 = iron(III)Oxide
FeO = iron(II)Oxide
 Remember!!!
R.N. is the charge, not
the subscript of the metal.
Naming Covalent Compounds
Mono – 1
 Di - 2
 Tri - 3
 Tetra - 4
 Penta - 5

Hexa – 6
 Hepta - 7
 Octa - 8
 Nona - 9
 Deca - 10

Naming Covalent Compounds

Step 1
Identify the number of
atoms in the first element
Ex. H2O two H atoms
Naming Covalent
Compounds

Step 2
Identify the number of
nd
atoms in the 2 element.
Ex. H2O one O atom
Naming Covalent
Compounds
Step 3
Name the compound with
the appropriate prefixes.
Ex. H2O
dihydrogen monoxygen

Naming Covalent
Compounds

Step 4 add an -ide ending
to the second element
Ex.
Dihydrogen monoxide
Empirical Formula
The simplest chemical formula
of a compound.
 Different covalent compounds
can have same empirical formula

Ch. 4.4