Transcript Ch 6 Chemical Names & Formulas

Ch 6 Chemical Names &
Formulas
P132 Addison Wesley Chemistry
Contents
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6.1 Introduction to Chemical Bonding
6.2 Representing Chemical Compounds
6.3 Ionic Charges
6.4 Ionic Compound
6.5 Molecular Compounds and Acids
6.6 Summary of Naming + Formula
Writing
6.1 Introduction to Chemical
Bonding
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Molecules & Molecular Compounds
Contents
Monoatomic
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Only noble gases exist as isolated atoms
Consist of single atoms
Ne, Ar, Ra
Diatomic
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Molecules that exist in pairs naturally
O2, H2, N2
Triatomic
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3 atoms of the same element
O3 - ozone
Molecule
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Smallest electrically neutral unit of a
substance that still has the properties of the
substance and consisting of one or more
atoms bonded together
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O + O  O2
H + H + O  H2O
Most atoms exist - in form of “molecule”
Compound
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A substance formed from the combination
of two or more elements in a definite
proportion by weight.
A compound can be one or more
molecules.
Molecular compounds
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Low melting pt.
Low boiling pt.
Many gas or liquid @ room temp.
Molecules composed of atoms of 2+
nonmetals
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Ex carbon monoxide – CO- diatomic
Ex water – H2O – triatomic
Ions & Ionic Compounds
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Ions- atoms or groups of atoms w/ ‘+’ or ‘-‘
charge
Form when loss or gain of electron from
atom
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Na = 11 p+ + 11 eIf loose 1eNa + = 11p+ + 10e-
Cation
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Any atoms w/ ‘+’ charge
Fewer e- than atom that formed it
Cation Naming
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Metallic elements names
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Name cation same as name of element
Sodium atom forms sodium cation
Do Not have same properties as atoms
Na atom explosive w/ H2O
 Na very stable in H2O
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Anion
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Atoms of nonmetallic elements game
electrons
Have ‘-’ charge
Anion Naming
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Nonmetallic elements name
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Not same as name
End in “-ide”
Sulfide-S2 Bromide-Br
Ionic Compound
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Compounds composed of cation and anions
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Metal cation + nonmetal anion
Ex NaCl
 Na+ + Cl Sodium Chloride – Table Salt
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Ionic Compound Properties
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Electrically neutral
‘+’ = ‘-‘ charge
usually solid crystals @ room temp.
melt @ high temp.
Table 6.1 Characteristics of
Molecular + Ionic Cmpds.
Characteristics
Molecular Cmpd
Ionic Cmpd
Representative Unit
Molecule
Formula unit
(balance of
oppositely charged
ion)
Types of Elements
Nonmetallic
Metallic combined
w/ nonmetallic
Physical State
Solid, Liquid, or Gas Solid
Melting Pt.
Low(usually below
300oC)
High(usually above
300oC)
6.2 Representing Chemical
Compounds
Contents
Chemical formulas
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Shows kinds + numbers of atoms in the
smallest representative unit of the
substance
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If the molecules of an element have more
than 1 atom a number is used as a subscript
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Ex O2- Oxygen
H2, F2, O2, N2, Cl2, Br2, I2
O3- Ozone
Molecular Formulas
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Shows kinds + numbers of atoms present in
a molecule of a compound
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Ex H2O- Water
Ex CO2- Carbon dioxide
Ex C2H6- Ethane
Does not show arrangement
Structural Formula
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ammonic gas (NH3)
H-N-H
H
Ball-and-stick molecular model
Methane – CH4
Penicillin
Formula Units
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Representation of ionic compounds
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(Na+) and (Cl-) form the solid NaCl (sodium
chloride)
Lowest whole number ratio of the ions
Charges not shown
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Magnesium chloride – Mg2+ and Cl – for
MgCl2
*Remember there is no such thing as a molecule
of NaCl or MgCl2 – they exist as a repeating
positively and negatively charged ions in 3D
patterns.
Laws of Definite Proportions
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In any sample of any chemical compound, the
masses of the elements are always in the same
proportion.
Means a sample of a chemical compound in our
lab is the same as a sample in someone else’s lab
by mass of elements in the compound.
Magnesium sulfide 100g =43.13g Mg + 56.87g S
Law of Multiple Proportions
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Whenever 2 elements form more than one
compound, the different masses of 1
element that combine w/ the same mass of
the other element are in the ratio of small
whole numbers.
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Example
A+B=C and 2A+B=D
 Then A is a proportion of 1:2
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Multiple Proportions
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Example
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H2O
H2O2
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8gO
16gO
O is a proportion 8:16 or 1:2 by mass
Helps if have mass of 1 proportion allow
easy way to obtain mass of other
6.3 Ionic Charges
Contents
Monatomic Ions
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ions consisting of only 1 atom
Metallic Elements
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tend to lose electrons (became positive)
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Group 1A => 1+ charge cation
Group 2A => 2+ charge cation
Group 3A => 3+ charge cation
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Aluminum only common group 3A metal
Group A Nonmetals
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tend to form anions
They tend to gain electrons (become negative)
Subtract the group # from 8 and make negative
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Group 7A => 1- charge anion
Group 6A => 2- charge anion
Group 5A => 3- charge anion
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3 nonmetals in this group
N3-, P3-, As3-
Group 4A
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Group 4A and O generally don’t form ions
Transition metals + the Z metals in 4A
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(Sn-tin + Pb-Lead)
Tend to form more than 1 cation
Transition metals
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Transition metals + the Z metals in 4A
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(Sn-tin + Pb-Lead)
Tend to form more than 1 cation
Table 6.3 p144
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Formulas + Names of Common Metal Ions
w/ more than 1 Ionic Charge
Polyatomic Ions
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Tightly bound groups of atoms that behave
as a unit and carry a charge.
Most end in ‘-ite’ or ‘-ate’
3 exceptions
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ammonium – (NH4+)
cyanide – (CN-)
hydroxide- (OH-)
‘ite’ vs. ‘ate’ ending
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‘ite’ signifies 1 less oxygen than ‘ate’ ion
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does not tell # of O atoms
Hydrogen at Beginning
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It is H+ cation combined w/ polyatomic
anion
It is algebraic sum of ionic charges
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H++ CO32- →HCO3- hydrogen carbonate
H++ PO43- → HPO42- hydrogen phosphate
H++ HPO42-→H2PO- dihydrogen phosphate
6.4 Ionic Compound
Contents
Writing Formulas for Binary
Ionic Compounds
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Binary compounds
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Compounds composed of 2 elements
KCL – potassium chloride (K+) + (Cl-)
Anion charge = cation charge
In writing formulas
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The positive charge cation must balance the
negative charge anion
The net ionic charge is zero
Cation (+) is written first
Anion (-) is written second
Binary Compound Examples
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Calcium bromide
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Ca2+ +Br- => CaBr2
2-2=0
took 2 Br to equal zero
1:2
rust-Iron (III) oxide
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Fe3+
+
O2=>Fe2O3
Make sure it is lowest whole # ratio
2:3 ratio
Naming Binary Ionic
Compounds
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CuO
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Metallic cation- copper
Nonmetallic anion- oxide
1:1 ratio
Oxide anion always 2- so copper cation must
balance it w/2Copper(П) oxide= CuO
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Transition metals may have 2 common ions
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Cu- 1++2+ - copper
Sn- 2++4+ - tin
Prefixes & Suffixes p 152
Binary Compounds
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All end in ‘ide’
Contain only 2 elements
One type-“molecular compound”
Prefixes represent # of atoms
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Carbon monoxide
Carbon dioxide
Polyatomic Ions
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End in ‘ite’ or ‘ate’
Most consist of 3 or more atoms
‘ite’ or ‘ate’ relate to the # of O atoms
‘ite’ is 1 less O than ‘ate’
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Nitrite ion-NO2- or nitrate ion NO3Neither ending represents a specific #
Ternary Ionic Compounds
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A compound containing atoms of 3
different elements
Usually contain a polyatomic ion
Ternary Ionic Compound
Formula
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1st write formula (symbol+ charge) for each
ion
then balance charges
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‘ate’ or ‘ite’ endings indicate a polyatomic
anion that includes O
‘ide’ only 2 common polyatomic ions end
in this
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hydroxide-(OH-)
cyanide-(CN-)
NH4+- Ammonium
Calcium nitrate
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(Ca2+) + (NO3-)
Ca2+ + NO3-  Ca(NO3)2
Parenthesis tell that more than 1 of the
polyatomic ion are needed – they keep it
together as a unit
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Parenthesis not needed if only 1 polyatomic
ion
Lithium carbonate
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Li+ - lithium cations
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CO32- - carbonate anions
Li+ + CO32-  Li2CO3
Naming
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1st recognize polyatomic ion
Name cation in 1st positon
Follow it w/ name of anion
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K2Cr2O7 – potassium dichromate
K2 – cation potassium
 Cr2O7 – anion dichromate
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6.5 Molecular Compounds and
Acids p 158
Contents
Binary Molecular Compounds
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Composed of 2 nonmetallic elements
Because composed of molecules ionic
charges are not used to assign formulas or
names
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When 2 nonmetallic elements often
combine in more than 1 way
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CO – carbon monoxide
CO2 – carbon dioxide
Prefixes help distinguish different
compounds
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Tell how many atoms
Mono- 1, di- 2, tri-3…p159
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All end in ‘ide’ same as binary ionic
compounds
Sometimes the vowel @ end of prefix is
dropped as in monoxide
Writing Formulas (given names)
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Use prefixes to tell subscript of each
element
Write correct symbols for the 2 elements
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Tetraiodine nonoxide – I4O9
Naming Common Acid
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Acids are compounds that produce H+ ions
in H2O
Consider them a combination of anions
connected to as many H+ ions needed to
make electrically neutral
Common Acids
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Hydrochloric acid –HCl
Sulfuric acid – H2SO4
Nitric acid – HNO3
Acetic acid – H3PO4
Phosphoric acid – H2Co3
6.6 Summary of Naming +
Formula Writing
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p 161 Figure 6.21 – naming flowchart
Contents
Acids
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If 1st compound is an H it is an acid
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HNO3 – Nitric acid
2 Elements (Not an Acid)
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2 elements
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binary compound – ends in ‘ide’
1st part is a metal and Group A element then just
name the ions (BaS – barium sulfide)
1st part is a metal and not a Group A element then
name the ions and use Roman numerals w/ the cation
(FeCl2 – iron (II) chloride
1st part is not a metal then it is a binary molecule so
use prefixes in the name (N2O3 – dinitrogen trioxide)
More Than 2 Elements (Not an
Acid)
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compound contains a polyatomic ion
name generally ends in ‘ite’ or ‘ate’
1st part is a Group A element then name the
ions(LiCO3 – lithium carbonate)
1st part is not a Group A then name the ions
+ use a Roman numeral w/ the cation
(CuSO4 – copper (II) sulfate)
Chemical Formula Rules
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In an ionic compound, the net ionic charge = 0
An ‘ide’ ending generally is a binary compound
An ‘ite’ or ‘ate’ ending means there is a
polyatomic ion that includes O in the formula
Prefixes in a name generally indicate that the
compound is molecular
Prefixes show the # of each kind of atom in the
molecule
A Roman numeral after a cation shows the ionic
charge of the cation
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p 162 Figure 6.23 Chemical formula
flowchart
Contents
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6.1 Introduction to Chemical Bonding
6.2 Representing Chemical Compounds
6.3 Ionic Charges
6.4 Ionic Compound
6.5 Molecular Compounds and Acids
6.6 Summary of Naming + Formula
Writing