Chem Lab Methods. Chemical Symbols Use the chemical symbol for each element Usually, the element abbreviations come from the word (He for Helium.

Naming and Writing IONIC Chemical Formulas

Chem Lab Methods

Chemical Symbols

Chemical Formulas: Writing

Use the chemical symbol for each element

Usually, the element abbreviations come from the word

(He for Helium or Ti for Titanium)

Some elements have just one letter, such as H for Hydrogen or N for Nitrogen

Chemical Formulas: Writing

Most elements have two letters Always capitalize the first letter and

use lower case on the second one.Example: Cobalt is Co

If you used two capitals (CO), it would be mistaken for Carbon Monoxide which has one Carbon (C) and one Oxygen (O)

Chemical Formulas: Subscripts

The subscript number specifies how many atoms of that element you have

N2 is a nitrogen molecule with two atoms

C2H4 has two carbons and four hydrogens

CO2 contains one carbon and two oxygens

If no number is listed, it means there is only one

http://en.wikipedia.org/wiki/File:Ethylene-CRC-MW-3D-balls.png

Example

C2H3Cl what elements and how many of each?

Example

C2H3Cl what elements and how many of each?

http://upload.wikimedia.org/wikipedia/commons/b/be/Vinyl-chloride-2D.png

Example

H2SiCl2what elements and how many of each?

Example

H2SiCl2what elements and how many of each?

http://upload.wikimedia.org/wikipedia/commons/9/9f/Dichlorosilane-2D-stereo.png

http://upload.wikimedia.org/wikipedia/commons/c/cd/Dichlorosilane-3D-balls.png

Chemical Formulas: Coefficients (numbers in front)

CH4 what elements and how many of each?


CH4 => methanewhat elements and how many of each?

http://upload.wikimedia.org/wikipedia/commons/1/1f/Methane-CRC-MW-3D-balls.png


When there are large numbers in front, that tells you how many molecules there are.

For example 3CH4 =




For example 3CH4 = 3 methane molecules

12NaOH = ?






For example 3CH4 = 3 methane molecules

12NaOH = 12 different Sodium Hydroxide units

http://upload.wikimedia.org/wikipedia/commons/6/63/Sodium-hydroxide-crystal-3D-vdW.png




Practice

Counting Atoms

Definitions

Nomenclature: Choosing of names for things Naming procedure

Ionic Compound: Atoms held together by ionic bonds

Binary Compound: Chemical compound made of atoms

from two different elements

Naming: Binary Ionic Compounds

Metal element name first

Then the non-metal element name, but the ending is changed to -ide

Example: CaCl2 would be called calcium chloride

Example: Ag2O would be called… silver oxide

Practice

Naming Binary Compounds

Ionic Formulas: Developing

Example:

Compound name - Magnesium chloride …What is the formula?


Magnesium Chloride =

Mg+2 Cl-1

What charge ion would each atom

form?

How many of each to make a neutral compou

nd?

Ionic Formulas: Developing Magnesium Chloride: Mg+2 and Cl-1

The charge of the final compound must be neutral.(The charges must balance)▪ Need TWO Cl-1 ions to balance one Mg+2 ion▪ (2 x -1) = (1 x +2) = 2 minus balances 2 plus

(Criss Cross!) Mg1 Cl2

MgCl2


Magnesium Chloride = 1 Mg+2 + 2 Cl-1 => MgCl2

Mg+2 Cl-1


Example: Compound name Lithium sulfide …What is the formula?


Lithium Sulfide=

Li+1S-2


form?


nd?

Ionic Formulas: Developing Magnesium Chloride: Li+1 and S-2

The charge of the final compound must be neutral.(The charges must balance)▪ Need TWO Li+1 ions to balance one S-2 ion▪ (2 x +1) = (1 x -2) = 2 minus balances 2 plus

(Criss Cross!) Li2 S1

Li 2 S


Lithium sulfide = 2 Li+1 + 1 S-2 => Li2S

Li+1

S-2


Example: Compound name Aluminum oxide …What is the formula?


Aluminum Oxide=

Al+3O-2


form?


nd?

Ionic Formulas: Developing Aluminum Oxide: Al+3 and O-2

The charge of the final compound must be neutral.(The charges must balance)▪ Need TWO Al+3 ions to balance THREE O-2 ions▪ (2 x +3) = (3 x -2) = 6 minus balances 6 plus

(Criss Cross!) Al2 O3 Al 2 O3


Boron Oxide = 2 Al+3 + 3 O-2 => Al2O3

B+3 O-2


SUMMARY of approach: Determine what charge ion would

form from each element Decide how many of each charge are

needed to have a balanced (neutral) formulaOR do “Criss Cross”

Write formula Subscripts state how many of each ion

are needed

Ionic Formulas: KEY POINT

Ionic compound formula describes: One “unit” of the chemical

compound Thus, it is called a “formula unit”

Important definition Example: 3 CaCl2

Three “formula units” of calcium chloride

Practice

Writing (Balanced) Chemical Formulas

Ionic Formulas: Continued….

Two more details:

Complex ions: contain more than one element

Transition metals: ionic charges can vary

Ionic Formulas: Complex Ions

Examples: Acetate is (C2H3O2)-1

▪ Whole group has -1 ionic charge

Carbonate is (CO3 )-2


The ENTIRE group has one ionic charge

Acts like a single-atom ion of the same charge

List of common complex ions on the back of your periodic table

Ionic Formulas: Complex Ions

All but ONE of the common complex ions are negative Phosphate is (PO3)-3


Chlorate is (ClO3 )-1


THE positive complex ion (worth memorizing) is: Ammonium (NH4)+1

Ionic Formulas: Developing Magnesium Phosphate: Mg+2 and (PO4)-3

The charge of the final compound must be neutral.(The charges must balance)▪ Need THREE Mg+2 ions to balance TWO (PO4)-3 ions

▪ (3 x +2) = (2 x -3) = 6 minus balances 6 plus

(Criss Cross!) Mg3 (PO4) 2

Mg 3 (PO4)2

Ionic Formulas: Transition Metals

Ionic charge can vary

How do you know? Listed on Periodic Table “Clue” in name

Examples of naming for metals with multiple charges

Element Cation Name Pronounced

Copper Cu+

Cu2+

Iron Fe2+

Fe3+

Lead Pb2+

Pb4+

Tin Sn2+

Sn4+



Copper Cu+ Copper (I) copper one

Cu2+

Iron Fe2+

Fe3+

Lead Pb2+

Pb4+

Tin Sn2+

Sn4+




Cu2+ Copper (II) copper two

Iron Fe2+

Fe3+

Lead Pb2+

Pb4+

Tin Sn2+

Sn4+





Iron Fe2+ Iron (II) iron two

Fe3+ Iron (III) iron three

Lead Pb2+

Pb4+

Tin Sn2+

Sn4+





Iron Fe2+ Iron (II) iron two

Fe3+ Iron (III) iron three

Lead Pb2+ Lead (II) lead two

Pb4+ Lead (IV) lead four

Tin Sn2+ Tin (II) tin two

Sn4+ Tin (IV) tin four

Ionic Formulas: Transition Metal Example

Write the chemical formula for Iron (II) Oxide

Step One: Determine the charges Iron (II) = Fe2+ and Oxide = O2-

Step Two: See how to balance the charges

Step Three: Find the combination that balances

Iron (II) Oxide = FeO

Ionic Formulas: Transition Metal Example

Write the chemical formula for Lead (II) Nitride

Step One: Determine the charges Lead (II) = Pb+2 and Nitride = N-3

Step Two: See how to balance the charges

Step Three: Find the combination that balances

Lead (II) Nitride = Pb3 N2

How do you know if you use Roman numerals? Do not use Roman Numerals for groups 1 or 2 as

they are always (+1) and (+2) accordingly.

K = +1 and Ca = +2+1

+2

How do you know if you use Roman numerals? Do not use Roman numerals for transition

metals that always form the same charge ion. Ag = +1 and Zn = +2 and Cd = +2

Practice

Ionic Compound Formula Writing (all types)

Chem Lab Methods. Chemical Symbols Use the chemical symbol for each element Usually, the element abbreviations come from the word (He for Helium.

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