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Naming Ionic Compounds
• • • NaF LiCl MgO -
Naming Ionic Compounds
• • • NaF LiCl Sodium Ion and Fluor ide ion Lithium Ion and Chlor ide Ion MgO Magnesium Ion and Ox ide Ion
Naming Ionic Compounds
• • • NaF LiCl MgO Sodium Fluor ide Lithium Chlor ide Magnesium Ox ide
More Practice
Cd(OH) 2 Na 2 SO 4 Cadmium Sodium Sulfate Hydroxide Ca(ClO) 2 Calcium Hypochlorite Na 2 SO 3 Sodium Sulfite AgCN Silver Cyanide KClO 4 Potassium Perchlorate
Ions You Should Know
http://sest.vsu.edu/~vvilchiz/ionsacids.htm
Properties of Molecular & Ionic Compounds
•
Chemical Substances; Formulas and Names
Naming simple compounds
Chemical compounds are classified as
organic
or
inorganic . Organic compounds
are compounds that contain carbon combined with other elements, such as hydrogen, oxygen, and nitrogen; they do not contain metals.
Inorganic compounds
are compounds composed of elements other than carbon and usually contain at least one metal atom.
Chemical Formulas; Molecular
•
Substances
Organic compounds
An important class of molecular substances that contain carbon is the
organic compounds
.
Organic compounds make up the majority of all known compounds. The simplest organic compounds are hydrocarbons, or compounds containing only hydrogen and carbon. Common examples include methane, CH 4 , ethane, C 2 H 6 , and propane, C 3 H 8 .
Naming Covalent Compounds
A
covalent compound
as we said before is formed by sharing electrons between 2 nonmetals or metalloids.
These compounds are usually
molecular
and are named using a
prefix system
.
When naming these compounds name the element further to the left (in the periodic table) first, then the one on the right.
Naming Covalent Compounds
You name the first element using the exact element name.
Name the second element by writing the root of the element’s name and add the suffix “–ide.” If there is more than one atom of any given element, you add the Greek prefix denoting how many atoms of that element are present.
lists the Greek prefixes used.
If only one atom of the second element is present it gets the prefix “mono”
Naming Covalent Compounds
Here are some examples of prefix names for binary molecular compounds.
PF 5 SO 2 SF 6 N 2 O 4 CO phosphorus
penta
fluoride sulfur sulfur
di di
oxide
hexa
nitrogen carbon fluoride
tetr mono
oxide xide
Naming Acids
are traditionally defined as compounds that could donate an H + ; however, they are acids only in the presence of water. In other
words before they enter the liquid they are covalent compounds and they are NOT acids .
There are two main types of acids:
Binary acids
consist of a hydrogen ion and any single anion. For example, HCl is hydrochloric acid.
An
oxoacid
is an acid containing hydrogen, oxygen, and another element. An example is a HNO 3
, nitric acid. (see Figure 2.23)
Naming Acids
• •
Binary Acids
– Start with the prefix “Hydro” which represents the Hydrogen, followed it with the root of the name of the second element and append the ending –oic acid.
Oxoacids
– Use the root of the “E” element if the ion taking part in the acid had an ending in –ate to the root append the ending –ic acid, if it ends on –ite then append the ending –ous acid. If the ion had a prefix use the same prefix.
Naming Acids
• Examples: – – – – – – – HCl(g) Hydrogen Chloride HCl(aq) Hydro Chlor ic Acid H 2 S(g) Dihydrogen Sulfide H 2 S(aq) Hydro Sulf ic Acid H 3 PO 4 (aq) Phosphor ic Acid HClO4(aq) Per chlor ic Acid HClO(aq) Hypo chlor ous Acid
Ionic Compounds Formulas
• How do we know how many atoms of each ion we need?
– A simple crossing of the charges can answer that question about 90% of the time.
• Example: Mg 2 + and PO 4 3 Mg 3 ( PO 4 ) 2 Check the charges… 3 x (+2) = +6 2 x (-3) = -6 – When they combined they cancel to yield a neutral compound.
Ionic Compounds Formulas
• • The crossing technique does not work if the magnitude of the charges is the same Example: Mg 2 + and CO 3 2 Mg 2 ( CO 3 ) 2 This is incorrect since we want the lowest ratio possible which is 1:1 to yield MgCO 3
Ionic Compounds Properties
• Ionic compounds have properties completely different from their component elements.
– Example: Table Salt (NaCl) • Sodium (Na) in the presence of water reacts violently heating up the water and producing hydrogen if the temperature of the water is high enough the hydrogen can ignite explosively.
• Chloride (Cl) Green poisonous and corrosive gas. If inhaled will destroy the nasal passages then dissolve in the stomach producing high concentration of hydrochloric acid which will destroy the stomach lining producing ulcers.
• Salt (NaCl) posses none of the properties mentioned above.
Ionic Structure
•Ions form a 3-D lattice.
•The coulombic (electrostatic) attraction is so high that in order to separate one ion from the lattice requires a lot of energy ( D H latt ).
•The lattice energy depends on charge and size of the ions.
Lattice Energy
• • • Since the lattice energy is an electrostatic interaction the more separated the charges are the weaker the interaction is.
– Bigger ions have lower lattice energies The higher the charge of the ions the stronger they will attract ions of the opposite charge.
D
H latt
q
1
q
2
r
12 When size and charge point to opposite trends the charge will outweigh the size.
– From smallest atom to biggest atom there is only 1.7x factor. From a +1 to +2 that is already a 2x factor.
Properties of Ionic Substances
• • Dues to the charged interaction a blow to a crystal leads to the possibility of splitting the crystal since we will force like charged particles to interact.
Ionic compounds have high melting/boiling points since in order to move the ions from their respective spots it will require breaking the lattice.
Ionic Solutions
• However, if we do melt an ionic compound it will be able to conduct current.
• When ionic compounds are placed in a solvent the produced solution conducts electricity. The higher the number of ions the higher the conductivity.
• More when we cover chapter 4.
Naming Hydrates
A
hydrate
is a compound that contains water molecules weakly bound in its crystals. Hydrates are named from the anhydrous (dry) compound, followed by the word “hydrate” with a Greek prefix to indicate the number of water molecules per formula unit of the compound.
For example, CuSO 4
.
5H 2 O is known as
copper(II)sulfate pentahydrate. (see Figure 2.24)
Determining Chemical Formulas
• Determining both empirical and molecular formulas of a compound from the percent composition.
The percent composition of a compound leads directly to its empirical formula.
An
empirical formula
(or simplest formula) for a compound is the formula of the substance written with the smallest integer (whole number) subscripts.
•
Determining Chemical Formulas
The
percent composition
of a compound is the mass percentage of each element in the compound.
We define the
mass percentage
of “A” as the parts of “A” per hundred parts of the total, by mass. That is,
mass % " A"
mass of " mass of A" in whole the whole
100 %
•
Mass Percentages from Formulas
Let’s calculate the percent composition of butane, C 4 H 10 .
First, we need the molecular mass of C 4 H 10 .
4 carbons @ 12.0
amu/atom
48.0
amu 10 hydrogens @ 1.00
amu/atom
10.0
amu 1 molecule of C 4 H 10
58.0
amu
Now, we can calculate the percents.
% C
48.0
amu C 58 .
0 amu total
100 %
82 .
8 % C % H
10.0
amu 58 .
0 amu H total
100 %
17 .
2 % H
Determining Chemical Formulas
• Determining the empirical formula from the percent composition.
Benzoic acid is a white, crystalline powder used as a food preservative. The compound contains 68.8% C, 5.0% H, and 26.2% O by mass. What is its empirical formula?
In other words, give the smallest whole-number ratio of the subscripts in the formula
C x H y O z
Determining Chemical Formulas
• Determining the empirical formula from the percent composition.
For the purposes of this calculation and making calculations simpler, we will assume we have 100.0 grams of sample benzoic acid.
Then the percentage of each element equals the mass of each element in the sample.
Since
x
,
y
, and
z
in our formula represent mole-mole ratios, we must first convert these masses to moles.
Determining Chemical Formulas
Determining the empirical formula from the percent composition.
Our 100.0 grams of benzoic acid would contain:
68 .
8 g C
1 mol C 12.0
g
5 .
73 ( 3 ) mol C 5 .
0 g C
1 mol H 1.0
g
5 .
0 mol H 26 .
2 g O
1 mol O 16.0
g
1 .
63 ( 7 ) mol O This isn’t quite a whole number ratio, but if we divide each number by the smallest of the three, a better ratio might emerge.
Determining Chemical Formulas
Determining the empirical formula from the percent composition.
Our 100.0 grams of benzoic acid would contain:
5 .
73 mol C
1.63(7)
3.50
5 .
0 mol H
1.63(7)
3.0
1 .
63 ( 7 ) mol O
1.63(7)
1.00
now it’s not too difficult to see that the smallest whole number ratio is 7:6:2. The empirical formula is C 7 H 6 O 2 .
Determining Chemical Formulas
• Determining the
“true” molecular formula
from the empirical formula.
An empirical formula gives only the smallest whole number ratio of atoms in a formula.
The
“true” molecular formula
could be a multiple of the empirical formula (since both would have the same percent composition).
To determine the “true” molecular formula, we must know the
“true” molecular weight
of the compound.
Determining Chemical Formulas
• Determining the “true” molecular formula from the empirical formula.
For example, suppose the empirical formula of a compound is CH 2 O and its “true” molecular weight is 60.0 g/mol.
The molar weight of the empirical formula (the “empirical weight”) is only 30.0 g/mol.
This would imply that the “true” molecular formula is actually the empirical formula doubled 2(CH 2 O) or
C 2 H 4 O 2
Molecular and structural formulas and molecular models.
A model of a portion of a Sodium Chloride crystal.
Common Ions of the transition metals
List of Polyatomic Ions
Greek Prefixes for Covalent Compounds Nomenclature
Making and Acid
Molecular model of nitric acid.
Figure 2.24: Copper (II) sulfate.
Photo courtesy of James Scherer.
Naming Flow Chart
Naming Flow Chart II
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Naming Acids Flow Chart
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