Molecular Compounds & Acids

• Molecule – two or more atoms covalently bound together
• Diatomic molecule – two of the same atom bound together

• H, N, O, F, Cl, Br, I or the Magnificent 7
• H ave N o F ear O f I ce C old B everages
• These elements exist as diatomic molecules in their most stable state.
• For example:
– Br  Br
2
– I  I
2
– N  N
2
– Cl  Cl
2
– H  H
2
– O  O
2
– F  F
2

• Binary covalent compounds contain 2 nonmetals
• No Polyatomic Ions!!!!!
• No Charges!!!!

• Before you can name binary covalent compounds, you
MUST know the prefixes!
• Mono
• Di
• Tri
• Tetra
• Penta
• Hexa
• Hepta
• Octa
• Nona
• Deca
• 1
• 2
• 3
• 4
• 5
• 6
• 7
• 8
• 9
• 10

Rules for naming Binary Covalent Compounds ex. N
2
F
4
• Name the prefix for the number of atoms of the first element (ex. Di-)
• Then name the first element (ex. Dinitrogen)
• Name the prefix for the number of atoms of the second element (ex. Dinitrogen tetra-)
• Than name the root of the second element with the ending – ide
(ex. Dinitrogen tetrafluoride)

• If the 1 st prefix is mono….DROP IT!
– Ex. CO is carbon monoxide NOT monocarbon monoxide
• When the prefix ends in an o or a, and the name of the element begins with a vowel, the o or a is often dropped
– EX. CO
4 would be carbon tetroxide NOT carbon tetraoxide

• What is the name of N
2
O
4
?
 N
2
 di nitrogen
 O
4
 tetra oxide
 Since oxide begins with a vowel, we will
 drop the a in tetra
 Dinitrogen tetroxide

• Name SO
2
 S  mono sulfur
 But mono is with the 1 st element, so it will be dropped  sulfur
 O
2
 dioxide
 Sulfur dioxide

• Write the formula for dichlorine monoxide
 Dichlorine  Cl
2
 Monoxide  O
 Cl
2
O

• Write the formula for disulfur dichloride
 Disulfur  S
2
 Dichloride  Cl
2
 S
2
Cl
2

• Acids can be recognized because the start with H
• Examples
– HCl
– H
2
SO
4
– HI

• Acids are in aqueous solution (aq)
• For the purposes of this class, we will assume that if it begins with H, we will name it according to the rules of naming acids

• If the anion ends in – ide , the acid will be named…
• Hydro (root) – ic acid
• Examples
• HCl
• Hydrochloric acid
• HI
• Hydroiodic acid
• H
2
S
• Hydrosulfuric acid

• If you have an H plus an anion ending in – ate , the acid will be named…
• (root) – ic acid
• H
2
SO
4
• Sulfuric acid
• HNO
3
• Nitric acid
• H
3
PO
4
• Phosphoric acid
• Examples

• If you have an H plus an anion ending in – ite , the acid will be named…
• (root) – ous acid
• Examples
• H
2
SO
3
• Sulfurous acid
• HNO
2
• Nitrous acid
• H
3
PO
3
• Phosphorous acid

• When writing formulas for acids you MUST look at the charges of the anion and add as many hydrogens as needed to cancel out the negative charge (because hydrogen is
+1)
– Example : Phosphoric acid
– Phosphate = PO
4
-3
– So, phosphoric acid = H
3
PO
4

ate  ic ite - ous

• H
2
SO
3
• H
2
CO
3
• HF
• Nitrous acid
• Perchloric acid
• Iodic acid
• Sulfurous acid
• Carbonic acid
• Hydrofluoric acid
• HNO
2
• HClO
4
• HIO
3

• Three sets of rules, ionic, covalent, and acids
• To decide which to use, decide what the first substance is.
• If is a metal or polyatomic ion use ionic .
• If it is a non-metal use covalent .
• If it is hydrogen , use acid rules

• Some compounds trap water crystals when they form.
• These are hydrates.
• Both the name and the formula needs to indicate how many water molecules are trapped.
• In the name we add the word hydrate with a prefix that tells us how many water molecules.

• In the formula you put a dot and then write the number of molecules.
• Calcium chloride dihydrate =
CaCl
2

2
O
• Chromium (III) nitrate hexahydrate =
Cr(NO
3
)
3

6H
2
O

Mixed examples
(remember to figure out what type of compound it is 1 st !)
• KClO
2
• CO
2
• H
2
SO
4
• NH
4
Br
• CuCO
3
• Fe
2
O
3
• HClO
• Potassium chlorite
• Carbon dioxide
• Sulfuric acid
• Ammonium bromide
• Copper (II) carbonate
• Iron (III) oxide
• Hypochlorous acid

• Carbon tetrachloride
• Phosphorous pentachloride
• Aluminum oxide
• Copper (II) nitrate
• Chlorous acid
• Hydrophosphoric acid
• Iron (III) hydroxide
• CCl
4
• PCl
5
• Al
2
O
3
• Cu(NO
3
)
2
• HClO
2
• H
3
P
• Fe(OH)
3