The nuts and bolts of The nuts and bolts of basic chemistry!basic chemistry!

The nuts and bolts of The nuts and bolts of basic chemistry!basic chemistry!

Naming ionic compoundsNaming ionic compounds

Writing formulas of ionic compoundsWriting formulas of ionic compounds

Naming Ionic Compounds

• Cation goes first!

• Anion gets –ide for its ending.

• Polyatomic anion doesn’t need its ending changed.

• The cation is usually a metal.

• D-block cations have some special rules we’ll cover in a minute.

• Anions are on the right of the periodic table.

Examples• NaCl: Sodium Chloride

• Na3PO4: Sodium phosphate

• CaCl2: Calcium chloride

• KMnO4: Potassium permanganate

• Al2O3: Aluminum oxide

What should you What should you notice about these notice about these

names?names?

What should you What should you notice about these notice about these

names?names?1.1. The number of atoms of a particular type The number of atoms of a particular type

doesn’t influence the namedoesn’t influence the name2.2. The metal comes first.The metal comes first.3.3. Monatomic anions end in -ideMonatomic anions end in -ide

Writing Chemical Writing Chemical FormulasFormulas

Writing Chemical Writing Chemical FormulasFormulas

The subscript depends on the The subscript depends on the oxidation numbers of the ions!oxidation numbers of the ions!

Using Al Guenther’s Manipulatives

• Cut out the shapes of the ions on the sheet.

• Notice that each cation has a point for every +1 of charge. Each anion has a notch for each -1 of charge.

• Assemble ionic compounds so that no points or notches are unpaired.

NaCl is 1 sodium and 1 chloride ion

CaCl2 is 1 calcium and 2 chlorides

• Why? Because Ca has a 2+ oxidation number and it takes 2 chlorides, with 1- each, to make the compound neutral overall.

• Sodium has a 1+ oxidation number, and balances with chlorides in a 1 to 1 ratio.

Polyatomic ions• See page 226 of your textbook!• Treat polyatomic ions like any

other ion. The only difference is that you might need parentheses in your chemical formulas.

• Don’t replace ending with –ide!

Write the formula for Magnesium nitrate.

• 1. Magnesium, Mg, is 2+• 2. Nitrate is on p. 226.(Holt Modern

Chemistry, Blue edition) It’s NO3-.

• 3. It will take 2 nitrates to balance the magnesium.

• 4. MgNO32? NO Way! That looks like 32 oxygens!

• 5. Mg(NO3)2 solves the problem!

What about when you don’t have that “O32”

look?• You STILL need the parentheses to

clarify that you want multiple copies of the WHOLE polyatomic ion.

• Example: Mg(OH)2 ≠ MgOH2

Why not??

Practice with parentheses

• Write the formula for potassium hydroxide.

• Write the formula for calcium hydroxide.

• Write the formula for aluminum sulfate.

Answers…• The formula for potassium

hydroxide is KOH.• The formula for calcium hydroxide

is Ca(OH)2

• The formula for aluminum sulfate is Al2(SO4)3

D-block Cations• D-Block metals can have more

than one oxidation number. See your periodic table.

• Bold print oxidation number is most common oxidation state.

• How do you know which one to use??

Naming D block cations in ionic compounds

YOU MUST INCLUDE THE OXIDATION NUMBER WHEN YOU

WRITE THE NAME OF THE COMPOUND!!

• Copper (I) chloride: CuCl

• Copper (II) chloride: CuCl2

Practice writing names of ionic compounds with d-

block cations• FeCl3• Fe2(SO4)3

• Cu2CrO4

• CuCrO4

• Sn(SO4)2

• SnSO4

Try these, and I’ll give you the answers after you try them. Don’t leave out the Roman numeral! If you do, it is WRONG!

How did you do?

• FeCl3• Fe2(SO4)3

• Cu2CrO4

• CuCrO4

• Sn(SO4)2

• SnSO4

• Iron (III) chloride• Iron (III) sulfate• Copper(I)Chromate• Copper(II)Chromat

e• Tin (IV) sulfate• Tin (II) sulfate

Formula MassFormula MassFormula MassFormula Mass

Calculating formula masses- Calculating formula masses- calculator optional calculator optional

Formula mass-easy rules!

• List the elements in the compound.• Multiply the mass of each element

by the number of atoms of that element in the formula.

• Add the products.• (Easy once you see it!)

Find the formula mass of BaF2

• Ba weighs 137.327• F weighs 18.998• There are 2 Fluorines in the

compound...2x18.998 = 37.996,• PLUS 137.327 for the barium =

175.323 gramspermole – OR 175.323 a.m.u.

What about one of the complicated looking

ones?• (NH4)2SO4?

• The key is to identify the number of each element in the compound.

• N? H? S? O?

The key is to identify the number of each element in the

compound.

• (NH4)2SO4?

• N = 2• H = 8 (comes from4x2)• One sulfur• O = 4

Number of each element TIMES element

mass• N 2 x 14 = 28• H 8 x 1 = 8• S 1 x 32 = 32• O 4 x 16 = 64• Add them up! 28 + 8 + 32 + 64 =

The formula mass of (NH4)2SO4 is

• 132 grams per mole, or 132 a.m.u.

Practice the easy ones on the sheet, #8-14.

Ready for a challenge? Try finding the mass of #35-42!

Significant figures• Yep, here we go again! If a

question is given to you with a number in it, you must pay attention to sigfigs when you answer that question. Beware careless rounding in calculating formula masses!