naming compounds and writing formulas. step 1 - determine the bond type metal atomsnon-metal atoms...
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Step 1 - Determine the Bond TypeMetal atoms Non-metal atoms
Metallic bonds Ionic bonds Covalent bonds
Ionic bonds – Form between metal and a non-metal atoms. Forms ions, not molecules. Covalent bonds – Form between 2 non-metals. Forms molecules.
Metallic bonds – Mixture of 2 metal atoms.
Naming Ionic Compounds
1. Name the first ion2. Name the second ion changing the suffix to
–ide.
Examples:NaCl Sodium Chloride
CalciumCaCl2Chloride
MgI2Magnesium iodide
Writing Ionic FormulasTwo simple steps:1. Write the symbol and charge of each ion2. Balance the charges using subscripts.
– What is the number of valence electrons?– What is the charge on the ION?
Magnesium chloride
Mg+2 Cl-1
Cl-1
MgCl2
Write the symbol and charge of each ion.Balance the charges by supplying subscripts. Subscripts tell how many of each atom is present.You need a second Cl-1 to balance the charges
Aluminum Sulfide Write the symbol and charge of each ion.Al+3 S-2
Balance the charges by supplying subscripts.In this case the charges do not evenly divide into each other. You must find the least common multiple. SIX
How many aluminums are needed to arrive at a +6 charge?
How many sulfurs are needed to arrive at a -6 charge?
2
3
Al+3 S-2
S-2
Al2S3
Polyatomic ions
• Polyatomic ion – Group of atoms that act as a unit and carry a charge.
CO3-2
carbonate
This ion is composed of one carbon and three oxygens and the entire group has a charge of -2.
Some Polyatomic Ions
SO4-2 Sulfate
SO3-2 Sulfite
ClO4-1 Perchlorate
ClO3-1 Chlorate
ClO2-1 Chlorite
ClO-1 Hypochlorite
PO4-3 Phosphate
C2H3O2-1 Acetate
OH-1 Hydroxide NO3
-1 Nitrate
NO2-1 Nitrite
You need to recognize these!!!
NH4+1 Ammonium
(only positive PI)
More examples:
How to Name Ionic Compounds with Polyatomic Ions
1. Name the first ion.2. Name the polyatomic
ion. – You just have to look
up the polyatomic ion on your sheet.
Na2CO3
Sodium carbonate
When you look at this compound you should recognize that this is NOT binary. There are THREE elements present. When you see this, immediately look for a polyatomic ion. CarbonateCarbonate is present here.
NH4Cl Name the first ion.
Ammonium Name the second ion.chloride
Notice that since the second ion is a nonmetal, the suffix changes to –ide.
(NH4)3PO4Name the first ion.
Name the second ion.Ammonium phosphate
Looks like a monster, but it’s really a pussycat.
How do you write formulas for ionic compounds with polyatomic ions?
Very much like writing formulas for Binary Ionic Compounds.
Two steps:
•Write the formulas/symbols of each ion.
•Balance the charges by using subscripts.
•If a subscript is needed for a polyatomic ion, it must be put in parentheses with the subscript on the outside.
Let’s do some!!
Aluminum nitrate First, you can tell from the name that there is a polyatomic ion present (nitrate). All binary ionic compounds have suffixes of –ide.
Write the formula/symbol and charge of each ion.
Al+3 NO3-1
Balance the charges by supplying subscripts.
Since Al is +3 and NO3 is -1, you need a total of 3NO3
-1 to balance one Al+3
Since you will need a subscript of 3 for NO3-1, you
need to put this in parentheses with the 3 outside.
Al(NO3)3
Silicon acetate Write the formula/symbol and charge of each ion.Si+4 C2H3O2
-1
Balance the charges by supplying subscripts. Since Si is +4 and C2H3O2 is -1, you will need 4 C2H3O2
-
1 to balance 1Si+4
Si(C2H3O2)4
Calcium phosphateWrite the formula/symbol and charge of each ion.
Balance the charges by supplying subscripts. Since Ca is +2 and PO4 is -3, you will need 3 Ca+2 to balance 2 PO4
-3
Ca+2 PO4-3
Ca3(PO4)2
Covalent Compounds
What are Binary Molecular Compounds?
• These compounds contain two elements (binary).
• The term “molecular” indicates that these elements are joined by a covalent bond.
• They must therefore be nonmetals.
• Bottom line – 2 elements – both nonmetals
• To name and write formulas for these, you must know some numerical prefixes.
Naming Covalent Compounds – you must use prefixes.
1 = mono 3 = tri 5 = penta 7 = hepta 9 = nona
2 = di 4 = tetra 6 = hexa 8 = octa 10 = deca
1.The first nonmetal only gets a numeric prefix when there is more than one. No prefix if there is only one.
2.The second element always gets a numeric prefix and always has a suffix of -ide
CO2
Carbon dioxide
CO
Carbon monoxide
N2O4
Dinitrogen tetraoxide
H2O
Dihydrogen monoxide
CCl4
Carbon tetrachloride
Name the first element. Since there is only one, no prefix is needed. The second element always gets a prefix and a suffix of –ide.
Name the first element. Since there are two present, the prefix “di” is needed. The second element always gets a prefix and a suffix of –ide.
Do you think it wise to BAN DHMO?
AlCl3What do you think about this one???
Be careful. This is a metal and nonmetal.
Always keep your Periodic Table in front of you for reference.
You may have been tempted to say “aluminum trichloride”. This is INCORRECT!
This is a binary IONIC compound. No prefixes are used. Simply aluminum chloride.
Given the names of binary molecular compounds, how do you write the formulas?
Very easy to do!!! The prefixes tell you how to write the formulas. DO NOT CONSIDER CHARGES. NONMETALS ARE ALL NEGATIVE SO TO USE CHARGES DOES NOT WORK!
Silicon dioxide
Diphosphorous pentachloride
Silicon and oxygen are both nonmetals.
The lack of a prefix on silicon means that there is only ONE silicon.
The prefix “di” in front of oxide means that there are TWO oxygens.
SiO2
Phosphorous and chloride are both nonmetals.
The prefix “di” means that there are TWO phosphorouses (Is that a word?)
The prefix “penta” before chlorine means that there are five chlorines.
P2Cl5
NO
Nitrogen monoxide Nitrogen and oxygen are both nonmetals.
The lack of a prefix on nitrogen means only ONE nitrogen.
The prefix “mono” on oxygen indicates ONE oxygen.
Isn’t this sooooooo easy!??