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Chapter 9 Notes, part I. Writing Ionic Formulas. Compounds. Up until now, we have only looked at single elements. There are only (to date) just over 100 elements, so how do we account for there being so many different types of stuff?. Compounds. - PowerPoint PPT Presentation
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Chapter 9 Notes, Chapter 9 Notes, part Ipart I
Writing Ionic Writing Ionic FormulasFormulas
CompoundsCompounds
•Up until now, we have only looked at single elements.
•There are only (to date) just over 100 elements, so how do we account for there being so many different types of stuff?
CompoundsCompounds•There are millions of different compounds—two or more elements that are combined chemically.
•The two types of compounds we will discuss in this chapter are ionic compounds and covalent compounds.
Ionic Ionic CompoCompouundsnds•Last chapter we discussed ions—elements that have a charge due to losing or gaining electrons.
•Ionic compounds are made of ions.
Ionic Ionic CompoCompouundsnds• Metals tend to form ions by losing
electrons, giving them an overall positive charge. These are called cations.
• Nonmetals tend to form ions by gaining electrons, giving them an overall negative charge. These are called anions.
Ionic Ionic CompoCompouundsnds•An ionic compound is
formed from a cation and an anion, which means they are usually formed from a metal and a nonmetal.
Ionic Ionic CompoCompouundsnds•Anions and cations can also
be made up of a group of elements bonded together that carry an overall charge.
•These groups of elements are called polyatomic ions.
Ionic Ionic CompoCompouundsnds•Even though an ionic
compound is made from charged particles, it is still electrically neutral.
•This means that its total charge is always EQUAL TO ZERO!!!
Chemical Chemical FoForrmulasmulas• SIDENOTE: The smallest part of
an ionic compound is called a formula unit—just like the smallest part of an element is called an atom.
• A chemical formula is like the recipe of a compound—it tells you the type and number of each element in the compound.
Writing ChemicWriting Chemicaal l FormulasFormulas
1) Write the symbol for the elements and their oxidation number, positive ion first (the metal).EX: For a compound of Magnesium and ChlorineEX: For a compound of Magnesium and Chlorine
Mg+2 Cl-1
Writing ChemicWriting Chemicaal l FormulasFormulas2) Criss cross the numbers and
write them as subscripts without the signs.
Mg Cl+2 -12 1
Writing ChemicWriting Chemicaal l FormulasFormulas3) If there is a one charge, do
not write it.
Mg1Cl2Mg Cl2
Writing ChemicWriting Chemicaal l FormulasFormulas4) If you have subscripts that
are multiples, reduce them down.
Pb O+4 -24 2
21
Writing ChemicWriting Chemicaal l FormulasFormulas5) If using polyatomic ions, put
parentheses if there are more than one.
Ca NO3
+2 -12 1( )
Writing ChemicWriting Chemicaal l FormulasFormulasHere’s an example of a
polyatomic that doesn’t have parentheses.
Na PO4
+1 -31 3
Practice These:
Barium and chlorineRubidium and nitrogen Lithium and phosphate Iron (III) and nitrateManganese (IV) and sulfur
BaCl2Rb3NLi3PO4
Fe(NO3)3
MnS2
Naming Ionic Naming Ionic CompoundsCompounds
Naming Ionic Naming Ionic CCompoundsompounds
For ionic compounds where the metal always has the same oxidation number,
1) Name the metal.EX: BaBrEX: BaBr22
Barium
Naming Ionic Naming Ionic CCompoundsompounds
For ionic compounds where the metal always has the same oxidation number,
2) Write the name of the non-metal, and change the end to –ide. Barium brom ine ide
EX: BaBrEX: BaBr22
Naming Ionic Naming Ionic CCompoundsompounds
If there is a polyatomic anion, then you do not change the ending: EX: Ca(NOEX: Ca(NO33))22
Calcium nitrate
Name These:
Na2O
MgCl2Na2CO3
Naming Ionic Naming Ionic CCompoundsompounds3)3)If a positive ion (a metal) can If a positive ion (a metal) can
have more than one oxidation have more than one oxidation number, you have to number, you have to designate its charge in the designate its charge in the name!name!
We do this by putting the charge We do this by putting the charge as a roman numeral in as a roman numeral in parenthesis between the parenthesis between the positive positive and negative and negative ion.ion.
Naming Ionic Naming Ionic CCompoundsompoundsWhy do we need to do that?
Name: Fe2O3
FeO
These both exist in nature, so we have to show which one we mean.
Naming Ionic Naming Ionic CCompoundsompounds
Fe2O3Name it:
Iron ox ygen ide ( ) III
-2
If this is true, then what was iron to begin with?
+3 Reverse criss cross to find the charge of
the iron:
Reverse criss cross to find the charge of
the iron:
Naming Ionic Naming Ionic CCompoundsompounds
Fe OName it:
Iron ox ygen ide ( ) II
-1
If this is not true, the numbers must have been reduced.
+2 -2
Naming Ionic Naming Ionic CCompoundsompoundsMetals that don’t need parentheses:Group I, II and IIIAZn, Cd (always +2) and Ag (always
+1)
Which means transition, inner transition and other metals do!
Naming Ionic Naming Ionic CCompoundsompoundsFinal flowchart of how to name:
Name the positive ion.
Does it need a roman numeral?
If so, reverse criss cross, if not, ignore.
Name the negative ion and:
If a nonmetal end in -ide; if not, end normally
Name these:
Na2S
CuCl2K2SO4
Pb(NO3)4