1.3 Ions and the Octet Rule
THE OCTET RULE
A full valence shell gives an element special stability. The first 18 elements have a full valence shell with
8 electrons with the exception of hydrogen and helium. Hydrogen and helium only have one ring of
electrons which holds at most 2 electrons. That means that hydrogen and helium reach stability with
only two electrons in its valence. When a valence shell is full it is known as a STABLE OCTET.
How can an atom reach this special stability??????
a. It can gain electrons
b. It can lose electrons
c. It can share electrons
Noble gases are stable because they have a full valence shell. All other elements want to be stable like
an noble gas. When the other elements gain or lose electrons to reach stability, they become
ISOELECTRONIC to a noble gas. Isoelectronic means they have the same number of electrons as a noble
gas on the periodic table.
THE FORMATION OF IONS
Ion- atom that has gained or lost electrons. The resulting entity has a positive or negative charge
The number of electrons an atom gains or loses depends on the number of valence electrons it has.
Gain
Lose
Electrons
Electrons
Negative
Positive
A. Positive Ions
-are made when metals(elements to the left of the staircase on the Periodic table) lose
electrons
-also known as CATIONS
-have the same name as their element example Na + is called a sodium ion
Example: Draw the Bohr diagram for an aluminum ion. Which noble gas is it
isoelectronic with
B. Negative Ions
-are made when non-metals(elements to the right of the staircase on the periodic table)
gain electrons
-also known as ANIONS
-these ions change ending of the name of the element to -ide . example Cl- is a chloride
ion
Example: Draw the Bohr diagram for Oxygen. Which noble gas is it isoelectronic with?
Multivalent elements
Elements that form more than one possible ion are called multivalent. Most of the transition metals are
multivalent.
Classical Naming system
-only for elements with two possible ions
-the latin name of the element is used with the ending -ous to represent the lower
valence and -ic to represent the higher valence
IUPAC Naming system
-uses a roman numeral in the ion's name to indicate the charge
Metal
Copper
Iron
Tin
Lead
Manganese
Ions
Cu+
Cu2+
Fe 2+
Fe 3+
Sn2+
Sn4+
Pb2+
Pb4+
Mn2+
Mn3+
Mn4+
Mn6+
Mn7+
Classical Name
Cuprous
Cupric
Ferrous
Ferric
Stannous
Stannic
Plumbous
Plumbic
n/a
IUPAC Name
Copper (I)
Copper (II)
Iron (II)
Iron (III)
Tin (II)
Tin (IV)
Lead (II)
Lead (IV)
Manganese (II)
Manganese (III)
Manganese (IV)
Manganese (VI)
Manganese (VII)
Polyatomic Ions
An ion made up of more than one atom that acts as a single entity is known as a polyatomic ion
Example NO2*see the list of polyatomic ions*
Ions in the Human Body
To be healthy, the body contains many ions in perfect balance.
Copy Table on pg. 21
Homework: pg. 22 #1-8