1. C2.1 ions & Molecules
An Ion is a charged particle that results when an atom gains or loses one or more electrons
Read Section 5.5
A molecule is a particle in which atoms are joined by covalent bonds (a bond that results from the sharing of outer electrons between non-metal atoms)
Read section 5.10

2. Ionic and molecular compounds
Ionic Compound (a metal & a non-metal)
They transfer electrons and become charged and the charges become attracted to one another
They are not physically bound together
Can commonly be broken up with a solution like water because water will go between them
In all ionic compounds, the positive and negative charges must be in balance
Molecular Compound (2 non-metals)
Their outer valence shells will overlap and they will share the electron
More difficult to break up because they are sharing electrons

3. Kinds of Ions There are three main kinds of ions
Basic ions have one charge (Li, H, Na) (Review Section 5.5)
Transitional metals have two charges, and will take on a different charge depending on what it is with (Fe, W)
Polyatomic ions are a group of elements acting as one and will take on one charge acting as one ion (Read Section 5.9)
Example: Nitrate Ion, NO3-, Ionic Charge of -1
Example Ammonium, NH4+, +1

4. Naming ionic compounds
Many ionic compounds are made up of two elements: a metal and a non-metal
Therefore, the names of ionic compounds have two parts
1. The first part refers to the metal ion in the compound
2. The second part refers to the non-metal ion in the compound
The name of the metal ion remains the same as the name of the neutral metal atom
The name of the non-metal changes to “ide”
Example:
Metal
Metal Ion
Non-Metal
Non-metal ion
Compound
magnesium
Magnesium ion
chlorine
Chloride ion
Magnesium chloride
aluminum
Aluminum ion
oxygen
Oxide ion
Aluminum oxide
For more information:

5. Writing chemical formulas: ionic compounds with one charge
The Crisscross method
Write the symbols of the elements and their ionic charges
Mg2+Cl-
Crisscross the numbers of the ionic charges so that they now become subscripts
MgCl2
3 . The chemical formula of magnesium chloride is MgCl2

6. Writing chemical formulas: ionic compounds with multiple charges
The same method applies, but you must pay attention to the name of the chemicals
Sometimes it will be given (i.e. iron(II) bromide)
Other times you will have to work from the chemical formula
Example on p. 199 (considering multiple ionic charges)

7. Practicing writing chemical formulas
In class assignment
Please submit at the end of class.

8. Molecular compounds Read Section 5.10 Between 2 non-metals
Molecular compounds both occur naturally and are produced synthetically. Some are beneficial; others are not
Molecular compounds are made up of molecules.
A molecule is a group of two or more atoms joined by covalent bonds
A covalent bond forms when two non-metallic atoms share electrons
Molecules that consist of only two atoms joined with a covalent bond are called diatomic molecules.

9. Elements that exist as diatomic molecules
Name of element
Chemical symbol
Formula of molecule
State at room temperature
Hydrogen H H2
gas
oxygen O O2
flourine F F2
bromine Br
Br2
liquid
iodine I I2
solid
nitrogen N N2
chlorine Cl
Cl2

10. C3.1 Naming molecular compounds (some common names)
Chemical Formula
Use/Occurrence
Water
H2O
The most commonly available molecular compound on earth
Ammonia
NH3
Used in window cleaners and in the production of fertilizers
Nitric Oxide NO
An air pollutant produced in the automobile engine when gasoline in burned
Hydrogen sulfide
H2S
An invisible gas with a distinctive “rotten egg” odor.

11. C3.1 Prefixes used for molecular compounds
# of Atoms
Sample molecular compound
Mon(o)- 1
Carbon monoxide, CO
Di- 2
Carbon dioxide, CO2
Tri- 3
Sulfur trioxide, SO3
Tetra- 4
Carbon tetrachloride, CCl4
Penta- 5
Phosphorus pentafluoride, PF5
The name of a molecular compounds includes prefixes to indicate how many atoms of each element are present (for example, dinitrogen pentoxide).
If there is only one atom of the first element, the prefix “mono” is omitted
The name of the last element ends in “ide”

12. C3.1 Sample problem: naming molecular compounds
Name the molecular compound with chemical formula PCI3
Step 1: Write the names of both elements in the same order as in the formula. Replace the ending of the second element with “ide” Phosphorus chlorine ide
Step 2: Add prefixes. Remember that the prefix “mono” is never used for the first element phosphorus tri chloride
The compound with chemical formula PCI3 is called phosphorus trichloride

13. Writing chemical formulas of molecular compounds
Given its name, writing the formua of a molecular compound is relatively simple. The prefixes in the name become the subscripts in the formula. For example, the molecular compound called sulfur dioxide has the chemical formula SO2