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Chemical Formulas

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Chemical Formula
a statement in chemical symbols that represents the composition of a substance
symbol in chemical formula
composition (elements)
subscripts in chemical formula
how many of each
H20
composition= H, O
amount= 2,1
2 Types of Chemical Formulas
Empirical and Molecular Formulas
Empirical Formulas
-simplest whole number ratio that elements can combine to form a compound
Molecular Formulas
- the exact number of atoms that are present in each elements for one molecule of a substasnce
Molecule
- the smallest particle of a substance that can exist and still have the composition and properties of a substance
2 Types of Molecules
Single Atom Molecules & Double Atom Molecules
Single Atom Molecules
- Noble Gases (elements and molecules
ex) Xenon
Double Atom Molecules
- two or more atoms of the same element from a molecule
- 7 Diatomic Elements
ex) Ozone (3 oxygen atoms)
Largest Group
- 2 or more diff. elements chemically combined like H20
Benzene (emp and molecular formula)
C6H6- molecular
CH- empirical
Acetylene (Ethyne)
C2H2- molecular
CH- empirical
Water
H20- molecular
H20- empirical
Ammonia
NH3- molecular
NH3- empirical
2 Types of Compounds
Ionic Compound and Molecular Compound
Ionic Compound
"compound"
Molecular Compound
"Molecule"
when metallic elements combine chemically with non-metallic elements...
one or more elemets is transferred to the non-metal
Metals
- 1, 2, 3 valence electrons
metals have a low...
-ionization energy (energy requiered to remove the most loosely held electrons)
- electronegativity (1, 1/2)
non-metals
1, 5, 6, 7 valence electrons
tend to have high...
ionization energies and electronegativety
rating scate for electronegativety
- ranks atoms ability to attract electrons in this bond
- 0-4 (best electronegatively-- Fluroine)
Ionic Compounds
- transfer electron for a stable octet
- crystal lattice (repeatin pattern in a solid phase)
Ionic Bond
- force of attraction
ex) NaCl
sodium transfers electron to cholorine
(metal to non-metal)
Empirical Formula
1:1 ratio
keeps building
What kind of formuals do ionic coumpounds have?
Empirical Formulas
More ions can join...
as long as the ratio is kept and continued
cation
(+) ion
anion
(-) ion
Rules for writing Binary Ionic Compounds
1) the least electromagnetic element goes first (the metal goes first- cation ion goes first)
2) Assign ionic charges (look at valence structure)
3) Assign enough of each atom so the compound is electrically neutral
# of (+)= # of (-)
what rule should you use?
criss-cross rule
metal, non-metal ends in
-ide
Hydrogen (metal/nonmetal)
non-metal
Ternary Ionic Compounds have...
PAI (poly atomic ions)
possibility types of Ternary Ionic Compounds
a) metal+ and PAI-
b) PAI+ and non-metal (ide)
c) PAI+ and PAI-
when can you drop parenthesis of PAI number?
when the number outside of the parenthesis is 1
never cahnge------ of PAI
subscriptions
oxidation number
state or charge
2 naming systems of ionic compounds of more that one oxidation numner (state)
1) Stock System
2) Latin Root- suffix
Stock System
- oxidation #
- IUPAC
- metal ( ) ending
ex) CU+1 chromate
copper (1) chromate
copper(11) chhromate
Latin Root
Latin root- ous (lowest possible charge)
- ic (next lowest)
ex) latin root
cuprous chromate
cuproc chromate
can you reduce within PAI
NO
Backwards Method
To find charge originally
After usign latin root for first too, then you go to the...
stock system
Instead of Hg+1
(hg+2) +2
Cr +2, +3
chromous
chomic
Cu +1, +2
Cuprous
Cupric
Fe +2, +3
Ferrous
Ferric
Sn +2, +4
Stannous
Stannic
Pb +2, +4
Plumbous
Plumbic
Sb +3, +5
Antimonous
Antimonic
Hg +1, +2
Mercurous
Mercuric
exists only as 2 (Hg+2)+2
O-1 O-2
O-1 can not be written cause you need 2 of them
peroxide (PAI)