Fundamentals of Chemistry 1030
Nomenclature Exercises

Purpose:

(1) Correctly identify elements from their symbol.

(2) Give the correct symbol for an element when given the name of that element.

(3) Use the periodic table to determine the ionic charge of a metal or nonmetal ion..

(4) Write the correct formula and name of an ionic or covalent compound.

(5) Write the correct formula and name of a compound containing a polyatomic ion.


In general, the reactivity of an element is determined by the valence electrons. Valence electrons are the electrons that occupy the the outer most shell (valence shell) in the electron configurations. The most stable elements obey the "octet rule" - that is, they have a filled valence shell containing eight electrons. The noble gases are a group of elements that have this type of electron arrangement, which explains why they are stable and unreactive. Other elements will gain or lose electrons in an attempt to obey the octet rule and become more stable. In the following excercises, you will see how how elements "use" their valence electrons to form compounds.


Electron Arrangements Electrons of similar energy are grouped in an energy level called a shell. Each electron shell can hold a different number of electrons. Shell 1 (the lowest energy level) can hold 2 electrons. Shell 2 can hold 8 electrons and shell 3 can hold 18 electrons. Electrons always fill the lowest energy level possible. Below are examples of the electron arrangement of some elements:


 
Number of Electrons
Electron Arrangement
Valence Shell Electrons
Na
11
2-8-1
1
Al
13
2-8-3
3
O
8
2-6
6
Cl
17
2-8-7
7
 

Forming Ions. When atoms of metals in groups 1A, 2A, or 3A react with atoms of nonmetals in groups 5A, 6A, and 7A, the metals lose electrons and the nonmetals gain electrons in their valence shells. We can use the periodic table to predict the number of electrons that will be gained or lost by each element.

Group 1A elements have 1 electron in their valence shell, so they will lose 1 electron.

Group 2A elements have 2 electrons in their valence shell, so they will lose 2 electrons.

Group 3A elements have 3 electrons in their valence shell, so they will lose 3 electrons.

Group 5A elements have 5 electrons in their valence shell, so they will gain 3 electrons.

Group 6A elements have 6 electrons in their valence shell, so they will gain 2 electrons.

Group 7A elements have 7 electrons in their valence shell, so they will gain 1 electron.

*Group 4A elements  with 4 electrons in their valence shell and do not gain or lose any electrons.

For example, aluminum (Al) is a group 3A metal which has 3 valence shell electrons.


 
Aluminum atom
Aluminum ion
Symbol
Al
Al3+
Electron arrangement
2-8-3
2-8 (full octect)
Number of protons
13 p+
13 p+
Number of electrons
13 e-
10 e- (loses 3 electrons)
Net ionic charge
0
3+
 

Chlorine (Cl) is an example of a group 7A nonmetal that gains electrons to fullfill the octet rule.

 
Chlorine atom
Chloride ion
Symbol
Cl
Cl-
Electron configuration
2-8-7
2-8-8 (full octect)
Number of protons
17 p+
17 p+
Number of electrons
17 e-
18 e- (gains 1 electrons)
Net ionic charge
0
1-
 

Writing Ionic Formulas

In an ionic formula, the total loss and gain of electrons is equal. The overall net charge is zero. So when a metal ion and a nonmetal ion combine to form a compound, the amount of positive charge must be made equal to the total amount of negative charge. To understand balancing charge in this experiment, we will use geometric shapes to help us determine the smallest whole number ratio that exists in order to give an overall charge of zero. In the example below, one magnesium ion is twice the size of the chloride ion, so it will take two chloride ions to balance the charge of one magnesium ion. This gives the ionic formula MgCl2.
 
 

When naming the compounds, write the metal name first, then the nonmetal ending in –ide. For example MgCl2 is named magnesium chloride.


Transition Metals

Most of the trasition metals can form multiple ions. For example, iron forms two ions, Fe2+ and Fe3+ . To distinguish between the two ions, a Roman numberal is used when naming compounds containing trasition metals as shown in the table below:
 
Ion
Name of Ion
Formula
Name of Compound
Fe2+
Iron (II) ion 
FeCl2
Iron (II) chloride
Fe3+
Iron (III) ion 
FeCl3
Iron (III) chloride
There are a few transition metals which only form one type of ion. These are zinc (Zn2+), silver (Ag+), and cadmium (Cd2+). Since the chatge on these elements do not vary, the Roman numeral notation is not used when naming their ions.

Polyatomic Ions

A polyatomic ion is a group of nonmetal atoms that has an overall charge (which is usually negative). Examples of some common polyatomic ions which you should become familiar with are given in the table below.


 
Formula
Names 
NO2-
Nitrite ion
NO3-
Nitrate ion
CO32-
Carbonate ion
HCO3-
Bicarbonate ion or hydrogen carbonate ion
SO32-
Sulfite ion
SO42-
Sulfate ion
HSO3-
Bisulfite ion or hydrogen sulfite ion
HSO4-
Bisulfate ion or hydrogen sulfate ion
PO33-
Phosphite ion
PO43-
Phosphate ion
OH-
Hydroxide ion
NH4+
Ammonium ion
 

To write the formula of a compound containing a polyatomic ion, detremine the number of each ion required to achive a charge balance just as you did earlier. If two or more polyatomic ions are needed, enclose the formula of the ion in parenthesis and wtire the subscript outside the parenthesis as shown in the example below:

A Handout is provided in  Lab