CHAPTER 9 Chemical Names and Formulas. Objectives for 9.1 (pgs 253-258) By the end of this section...
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Transcript of CHAPTER 9 Chemical Names and Formulas. Objectives for 9.1 (pgs 253-258) By the end of this section...
Objectives for 9.1 (pgs 253-258)
By the end of this section you WILL be able to…
• ID charges of monatomic ions by using PT
• Name ions• Define polyatomic ion and write names
and formulas of most common ones• ID two common endings for the names of
most polyatomic ions
Naming Ions
Monatomic-Ions formed from a single atom-Charge determined by number of valence
electronsNOTHING NEW! Cations-Positively charged-Form when elements LOSE electrons-Usually what type of elements?
Naming Cations-The name of the element followed by the
word ion.-For example:Na+ is sodium ion, Mg2+ is Magnesium Ion Anions-Negatively charged-Form when elements GAIN electrons-Usually form from what type of elements?
Naming Anions-Named for the element but have the
suffix –ideFor Example:Cl- is chloride N3- is nitride
Ions of Transition Metals (p. 255)
Since “s” and “d” valence electrons are available, transition metals may form cations with different charges (E.g. Fe2+ and Fe3+)
Stock System of naming uses a Roman numeral to designate the charge on the ion
-For Example:iron (II) and iron (III) – preferred over Classical
naming system If the transition metal only forms one ion you
do not have to use the stock system
Polyatomic Ions
Ions that are made up of two or more covalently bonded atoms yet still have a net charge
They behave like ions when bonding because of excess electrons, or excess protons
To form some of these ions, BOTH electrons to be shared come from one atom
What type of bond is this?-Coordinate Covalent
Oxyanions
Most of the common polyatomic ions are oxyanions
What do you think oxyanion means?-These anions contain different numbers of
oxygen atoms We will use the suffixes –ite and –ate to
show how many oxygen are on each
-ate indicates the ion with more oxygen atoms -ite indicates the ion with less oxygen atoms BFAt corner will help us identify how many
oxygen If central atom is in the BFAt corner 3 oxygen
atoms makes it an –ate 2 oxygen atoms is an –ite
If central atom is out of the BFAt corner 4 oxygen atoms makes it an –ate and 3 oxygen atoms is an -ite
Practice naming these…
SO42-, SO3
2-, NO2-, NO3
-, F-, ClO2-, ClO3
-
Respectively, they are sulfate, sulfite, nitrite, nitrate, fluoride, chlorite, and chlorate
You will need to memorize the charges!
Sometimes hydrogen appears at the beginning of an oxyanion
This just changes the name to hydrogen ___ ate (or ite)For Example:HSO3
-2 is called hydrogen sulfite
HSO4-2 is called________________
Prefixes
The prefix hypo- means less (think hypothermia)
This means there is one less oxygen than the oxyanion with the –ite ending.
For example:ClO- is called hypochloriteSO2
-2 would be called_________________
The prefix per- indicates that there is one MORE oxygen than the oxyanion with the –ate ending.
For Example:ClO4
- is called perchlorate
PO53- is called _______________
Time to do work!
Make flashcards for your polyatomic ions
Memorize their charges
Use the BFAt corner to determine if they are –ite or -ate
End of section 9.1 What are your questions?
9.2 Naming and Writing Formulas
Goals for this section…You will be able to…
Apply the rules for naming and writing formulas for binary ionic compoundsApply the rules for naming and writing formulas for compounds with polyatomic Ions
9.2 Naming and Writing Formulas for Ionic Compounds
Binary Compound-Compounds composed of two different
types of elements Naming Binary Ionic Compounds1. Write the name of the cation2. Write the name of the anion3. For metals with more than one oxidation
state, use the STOCK SYSTEM! For example: Iron (III) Chloride = FeCl3
Writing Formulas for Binary Ionic Compounds
Ion Charge Method uses charges of ions to determine quantity of each ion in a compound
The net charges of a compound = 0Steps to writing balanced Formulas1. Write the symbol and charge for each
ion present. Write the cation first then the anion.
Examples:Na+ Cl- or Ca2+ Cl-
2. Adjust subscripts by using the cross-over method.
Examples:Na+ Cl- or Ca2+ Cl-
NaCl CaCl2
3. Reduce if necessary. Subscripts should be in simplest whole number ratio.
1 1 21
The cross-over method also works for polyatomic ions. However, you must place parentheses around the entire ion to signify more than one.
Try these:Lead (II) SulfateBarium ChlorideIron (II) acetateAmmonium CarbonateTin (IV) chromate
Compounds with Polyatomic Ions
Write the symbol of the cation followed by the formula for the anion
Cross over to balance charges Place parentheses around the
polyatomic ion if there is more than one
Naming Compounds with Polyatomic Ions
Memorize formula and charges of polyatomic ions (quiz is coming up)
Name the cation (don’t forget about the stock system if needed)
Name the anion
Examples:A. Ca(OH)2
a. Calcium hydroxideB. FeSO4
b. Iron (II) sulfate
The reward of a thing well done is to have done it -Emerson
9.3 Naming and Writing Formulas for Molecular Compounds
Interpret the prefixes in the names of molecular compounds in terms of their chemical formulasApply the rules for naming and writing formulas for binary molecular compounds
Naming Binary Molecular Compounds
1. Name the first element in the formula2. Use the appropriate prefix to show how
many of that atom are present (see page 269)
3. Name the second element4. Use the appropriate prefix to show how
many of that atom are present5. Add the suffix –ide to show that it is a
binary compound
Writing Formulas for Binary Molecular Compounds
Use prefixes to tell you how many of each atom are present in the compound
Dinitrogen tetroxide N2O4
Iodine heptafluorideIF7
9.4 Naming and Writing Formulas for Acids and Bases
“If I set for myself a task, be it so trifling, I shall see it through. How else shall I have confidence in myself to do important things?”
-George Clason
Goals: Apply the rules for naming acids Apply the rules in reverse to write acids Apply the rules for naming bases
Acids and Bases Naming and Formula Writing
Acids-a substance that contains one or more
hydrogen atoms and produces hydrogen ions (H+) when dissolved in water
-The general form is HnX
- The name is dependent upon the name of the anion
Rules! Rule 1 – if the anion ends in “-ide”, the
acid name begins with “hydro” and ends with “-ic” (binary acid)
(E.g. HCl = hydro-chlor-ic acid)
Rule 2 – if the anion ends in “-ite”, the acid name ends with “-ous” (oxyacid). (no hydro)
(E.g. H2SO3 = sulfur-ous acid)
Rule 3 - if the anion starts with “hypo” and ends with “-ite”, the acid name starts with “hypo” and ends with “-ous” (E.g. HClO = hypo-chlor-ous acid)
Rule 4 – if the anion ends in “-ate”, the acid name ends with “-ic” (E.g. HNO3 = nitr-ic acid)
Rule 5 - if the anion starts with “per” and ends with “-ate”, the acid name starts with “per” and ends with “-ic” (E.g. HClO4 = per-chlor-ic acid)
I ate so much I felt icky
Naming Acids
Use the same steps we did when writing formulas only backwards
You should know your polyatomic Ions by now (they’re not going away)
Naming Bases
Bases- an ionic compound that produces
hydroxide ions (OH-) when dissolved in water
Naming Bases-Name bases as you would any other ionic
compound
Laws of Definite and Multiple Proportions
The Law of Definite Proportions - elements combine in a definite mass ratio regardless of the size of the sample produced (e.g. water is always 89% oxygen and 11% hydrogen by mass)
The Law of Multiple Proportions – whenever the same two elements form more than one compound, the different masses of one element that combine with a fixed mass of the other element are in a ratio of small whole numbers
Examples: H2O and H2O2 CO and CO2 N2O and N2O4