Naming Compounds and Formula Writing

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Transcript Naming Compounds and Formula Writing

Chapter 5
Naming Compounds
Writing Formulas
Naming Binary Ionic Compounds
Binary Compounds - 2 elements.
 Ionic - a cation and an anion.
 To write the names just name the two
ions.
 Easy with Representative elements.
 Group A
 NaCl = Na+ Cl- = sodium chloride
 MgBr2 = Mg+2 Br- = magnesium bromide

Naming Binary Ionic Compounds
The problem comes with the transition
metals.
 Need to figure out their charges.
 The compound must be neutral.
 same number of + and – charges.
 Use the anion to determine the charge
on the positive ion.

Naming Binary Ionic Compounds
Write the name of CuO
 Need the charge of Cu
 O is -2
 copper must be +2
 Copper (II) chloride
 Name CoCl3
 Cl is -1 and there are three of them = -3
 Co must be +3 Cobalt (III) chloride
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Naming Binary Ionic Compounds
Write the name of Cu2S.
 Since S is -2, the Cu2 must be +2, so
each one is +1.
 copper (I) sulfide
 Fe2O3
 Each O is -2
3 x -2 = -6
 2 Fe must = +6, so each is +3.
 iron (III) oxide
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Naming Binary Ionic Compounds
Write the names of the following
 KCl
 Na3N
 CrN

Sc3P2
 PbO

PbO2
 Na2Se
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Ternary Ionic Compounds
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Will have polyatomic ions
At least three elements
Just write the name of the element using the
front of the periodic table and the polyatomic
ion using the chart on the back of the table.
Examples of naming ternary ionic
compounds:

NaNO3 =
sodium nitrate

(NH4)2O = ammonium oxide
Ternary Ionic Compounds
name these:
LiCN
 Fe(OH)3
 (NH4)2CO3
 NiPO4

 CaSO4
 CuSO3
Writing Formulas
The charges have to add up to zero.
 Get charges for the 2 parts.
 Cations from location on p. table.
 Anions from p. table or polyatomic.
 Balance the charges by putting in
subscripts (small #’s on bottom right).
 Put polyatomic ions in parenthesis
before you give them subscripts.
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Writing Formulas
Write the formula for calcium chloride.
 Calcium is Ca+2
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Chloride is Cl-1
Ca+2 Cl-1 would have a +1 charge.
 Need another Cl-1
 Ca+2 Cl2-1
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 CaCl2
Write the formulas for these
Lithium sulfide
 tin (II) oxide
 tin (IV) oxide
 Magnesium fluoride
 Copper (II) sulfate
 Iron (III) phosphide
 gallium nitrate
 Iron (III) sulfide
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Write the formulas for these
Ammonium chloride
 ammonium sulfide
 barium nitrate
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Things to look for
If cations have (roman numeral), the
number is their charge.
 If anions end in -ide they are probably
off the periodic table (Monoatomic)
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Exceptions (Hydroxide (OH); Cyanide (CN)
are polyatomic.

If anion ends in -ate or -ite it is
polyatomic.
Molecular Compounds
Writing names and Formulas
Molecular compounds
made of just nonmetals
 smallest piece is a molecule
 can’t be held together because of
opposite charges
 can’t use charges to figure out how
many of each atom
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Easier
Ionic compounds use charges to
determine how many of each.
– Have to figure out charges.
– Have to figure out numbers.
 Molecular compounds name tells you
the kind of atoms.
 Uses prefixes to tell you the number
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Prefixes
1
2
3
4
5
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monoditritetrapenta-
6
hexa•7 hepta•8 octa•9 nona•10 deca-
Prefixes
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To write the name write two words
Prefix name Prefix name -ide
Prefixes
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To write the name write two words
Prefix name Prefix name -ide
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One exception is we don’t write mono- if
there is only one of the first element.
Prefixes
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To write the name write two words
Prefix name Prefix name -ide
One exception is we don’t write mono- if
there is only one of the first element.
 No double vowels when writing names
(oa oo)
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Ex. CO carbon monoxide
CO2 carbon dioxide
P2O5 diphosphorus pentoxide
Name These
N2O
 NO2
 Cl2O7
 CBr4
 BaCl2
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Write formulas for these
diphosphorus pentoxide
 tetraiodide nonoxide
 sulfur hexaflouride
 nitrogen trioxide
 Carbon tetrahydride
 phosphorus trifluoride
 aluminum chloride
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Acids
Writing names and Formulas
Acids
Compounds that give off hydrogen ions
when dissolved in water.
 Must have H in them.
 will always be some H next to an anion.
 The anion determines the name.
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Naming acids
If the anion attached to hydrogen is
ends in -ide, put the prefix hydro- and
change -ide to -ic acid
 HCl - hydrogen ion and chloride ion
 hydrochloric acid
 H2S hydrogen ion and sulfide ion
 hydrosulfuric acid
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Naming Acids
If the anion has oxygen in it
 it ends in -ate or -ite
 change the suffix -ate to -ic acid
 HNO3 Hydrogen and nitrate ions
 Nitric acid
 change the suffix -ite to -ous acid
 HNO2 Hydrogen and nitrite ions
 Nitrous acid
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Name these
HF
 H3P
 H2SO4
 H2SO3
 HCN
 H2CrO4
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Writing Acid Formulas/Naming
Hydrogen will always be first
 name will tell you the anion
 make the charges cancel out
 Starts with hydro- if no oxygen in the acid, -ide
ending becomes –ic
Ex. HCl = hydochloric acid
 no hydro, -ate ending from polyatomic ion
becomes -ic, H2SO4 = sulfuric acid
-ite ending becomes –ous, H2SO3 = sulfurous
acid
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Write formulas for these
hydroiodic acid
 acetic acid
 carbonic acid
 phosphorous acid
 hydrobromic acid
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