1. NIS – PHYSICAL SCIENCE
Lecture 88 – Lecture 89 – Lecture 90
Writing Formulas and Naming Compounds
Ozgur Unal

2. Writing Formulas and Naming Compounds
What is alchemy?

3. Binary Ionic Compounds
A binary compound is a compound that is composed of two elements.
Example: KI, NaCl, H2O … and more?
Oxidation number:
In an ionic compound:
Metals always lose electrons  positive ions
Nonmetals always gain electrons  negative ions
The charge on an ion is known as the oxidation number.
Cl-  oxidation number = -1
Na+  oxidation number = +1
What are the oxidation numbers of the ions of Ca, O, Mg, P, F, I, Li, N etc?
Check out Figure 20!!

4. Binary Ionic Compounds
Some elements can have more than one oxidation number!
Check out Table 3!!
Like all compounds, ionic compounds are neutral.
Example: CaCl2
Ca+2 has +2 charge
2 Cl- has -2 charge  net charge is +2-2=0!!
Perform the same exercise
for Al2O3.

5. Binary Ionic Compounds
Writing formulas:
1- Write the symbol of the element that has the positive oxidation number of charge.
2- Write the symbol of the element with the negative number.
3- To have a neutral compound, the positive charges have to balance negative charges.
Exercise 1: Write the formula for the binary ionic compound formed by Lead (IV) and Phosphorus
Exercise 2: Write the formula for the binary ionic compound formed by Iron (II) and Oxygen

6. Binary Ionic Compounds
Writing names:
1- Write the name of the positive ion.
2- If the positive ion has more than one oxidation number write the oxidation number using Roman numerals in parenthesis.
3- Write the root name of the negative ion.
4- Add the ending –ide to the root.
Example: NaCl  Sodium Chloride
Example: Fe2O3  Iron (III) Oxide
Example: Al2S3  Aluminum Sulfide
How about FeO?
How about CO2?

7. Compounds With Polyatomic Ions
Not all ionic compounds are binary!
Baking soda has the chemical formula NaHCO3  not binary!
Some ionic compounds are composed of more than two elements  polyatomic
A polyatomic ion is a positively or negatively charged, covalently bonded group of atoms.
A polyatomic ion contains two or more elements
Example: HCO3-
Check out Table 5!!

8. Compounds With Polyatomic Ions
In order to name a polyatomic ionic compound, we use the names of the positive and negative ions.
Example: K2SO4  Potassium sulfate
Name the following compounds:
Na2CO3
AgNO3
KOH
(NH4)3PO4
How do we write the formulas of these compounds?
Check out Figure 21!!

9. Compounds with Added Water
Some ionic compounds have water molecules as part of their structure  hydrates
A hydrate is a compound that has water chemically attached to its ions and written into its chemical formula.
Example: MgSO4 . 7H2O  Magnesium Sulfate Heptahydrate
Check out Table 6!!
How do you read CoCl2 . 6H2O?
You can remove water from these
crystals by heating them  anhydrous
CuSO4 . 5H2O  ??

10. Naming Binary Covalent Compounds
Remember binary covalent compounds?
Some pairs of nonmetals can form more than one compound with each other.
Example: NO, N2O, NO2, N2O5 etc..
Scientists use the Greek prefixes to indicate
how many atoms of each element are in
a binary covalent compound.
NO  Nitrogen monoxide
N2O  Dinitrogen monoxide
NO2  Nitrogen dioxide
N2O5  Dinitrogen pentoxide
Name the followings:
CO2 CO PH3 N2O3