Chapter 9 Chemical Formulas and Compounds
compounds - two or more elements combined in a definite formula
(recipe)
Eg. sugar
12 parts : 22 parts : 11 parts
carbon
hydrogen oxygen
12 atoms : 22 atoms : 11 atoms
C
H
O
= C12H22O11
p.186 Instant Practice
Acids and Bases
Acids
Bases
Turns blue litmus reD
Turns red litmus Blue
Sour
Bitter & slippery
Conducts electricity
Conducts electricity
Reacts with metals to produce hydrogen
gas
neutralization –
1
acid + base Æ salt + water
HCl + NaOH Æ NaCl + H-OH
H2SO4 + Ca(OH)2 Æ CaSO4 + 2 H-OH
* salts are very different from each other but they can all be
formed from an acid/base neutralization
indicators - a dye used to determine acidity
examples:
phenolphthtalein turns pink in acid but is clear if neutral or basic
bromthymol blue turns blue in and yellow in
Compounds are formed in two ways
• Ionic – when there is a transfer of electrons and ions are
formed.
• Covalent – when there is a co-operative sharing of electrons.
***even though the methods are different one thing is always the
same: CHEMICAL BONDS ARE FORMED BETWEEN THE OUTER
ELECTRON SHELLS OF EACH ATOM!!!
Ionic – when a metal loses as electron and becomes positively
charged ( + ) and a metal gains an electron to become negatively
charged ( - ). They are then attracted to each other and come
together like two magnets…they sort of bump up to each other.
2
Na Æ Na+ + e-
Cl + e- Æ Cl-
Na+ Æ Cl-
= NaCl
combining capacity - the number of electrons an atoms must give
up or gain to have a stable electron
arrangement.
e- gain : A Æ A-
e- loss : B Æ B+
3
Figure 9.12 Electron arrangements of the first elements. Transfer this
onto handout.
Review 9.2
Rules for writing Chemical Formulas
1) Write more metalic symbol first, less metalic next
2) Write combining capacities
3) Balance atoms
4) Balance combining capacities
Instant Practice
Compounds Of Ions With More Than One Combining Capacity.
Eg.
lead (IV) iodide
Pb+4
I-1
PbI4
copper (I) bromide
tin (II) iodide
Compounds with Polyatomic Ions
(many) (atoms)
Eg
4
Ca+2 OH-1
Ca(OH)2
Covalent Bonds- when two or more non-metals or two or more
metals share outer electrons
Comparison of Bonding Forms
5
Ionic
Metal atoms loses electron and
becomes (+)
( Na --> Na(+) + e(-) )
Non-metal atom gains electron and
becomes (-)
( Cl + e(-) --> Cl(-) )
Ions (+) (-) are attracted to each
other
Covalent
Atoms try to get 8 e(-) in outer shell to
be "happy"
Electrons are "shared" to form new
bonds
Naming Ionic compounds
Metal - non-metal root - ide
Eg.
Na+1
Cl-1
(sodium) (chloride)
K+1
Br-1
(Potassium) (Bromide)
More than 1 combining capacity?
Pb (+4)
I (-1)
PbI4
Lead (IV) iodide
Fe +3
O26
Fe2O3
Iron (III) oxide
Naming Covalent Molecules
Prefix - more metallic prefix - less
metallic root- ide
Prefixes:
1)
2)
3)
4)
5)
Eg.
a)
b)
-mono
- di
- tri
- tetra
- penta
C………O
Carbon monoxide
C………CI4
Carbon tetra-chloride
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