Name_____________________________________Date___________Period_______
I Want My Octet!
Everybody wants
to be like me!
Background: All elements want to be like the noble gases. The outer
shell, or valence shell of a noble gas is full of electrons. To be full, a valence shell
must contain 8 electrons. Today you will help atoms get their octets by adding or subtracting electrons
to make IONS.
On your paper, draw a Bohr model of aluminum
How many electrons are in the valence shell of aluminum? ________
How many electrons would this atom prefer to have in its valence shell? _______
Do you think aluminum would rather gain 5 electrons or lose 3 to get its octet? ____________
Add or subtract electrons from your Bohr model to give it an octet. Now that the number of electrons has
changed, the aluminum atom is called an aluminum ION. Fill in the information for this ion below:
Number of protons in ion = _______p+
Number of electrons in ion= _______eWhich particle is there more of? _________________ How many more of that particle are there? ________
What is the charge (oxidation number) of the aluminum ion? ___________________
Next draw the Bohr model of chlorine. Then fill in the information for the chlorine ion below:
Valence electrons = ______ Rather gain or lose? ________________ How many? _________
Add or subtract electrons from your model to give chlorine its octet. Then fill in the
information below:
Number of protons = _______ Number of electrons = _______ Oxidation number (charge) =_______
Next draw the Bohr model of nitrogen. Then fill in the information for the nitrogen ion below:
Valence electrons = ______ Rather gain or lose? ________________ How many? _________
Add or subtract electrons from your model to give chlorine its octet. Then fill in the
information below:
Number of protons = _______ Number of electrons = _______ Oxidation number (charge) =_______
You can also use the group number to determine the number of valence electrons.
For example, Selenium is in group 16, so it has _________ valence electrons. To obtain its octet, Selenium will
gain _______ electrons. Once it becomes an ion, selenium will have ______ protons and ______ electrons.
There are 2 _______________ (more or less) electrons than protons, so the charge on the ion is __________.
Fill in the missing information for each ion below. The selenium example has been completed for you:
Element
Group # Valence
Gain or
Gain/lose
# of p+
# of eOxidation #
electrons
lose e ?
how many? in ion
in ion
(Charge)
Selenium
Rubidium
Bromine
16
6
Gain
2
34
36
-2
Element
Group #
Valence
electrons
Gain or
lose e-?
Gain/lose
how many?
# of p+
in ion
# of ein ion
Oxidation #
(Charge)
Tellurium
Gallium
Tin
Arsenic
Calcium
Now use the information from your table above to write the oxidation number for elements in
each group on the periodic table below: Group 15 has been completed for you (All elements in
group 15 have a charge of -3).
-3
Extra Credit:
Create a song, poem, or graphic organizer to help you remember the oxidation numbers for the
groups on the periodic table. Write it in the space below and present it to the class for bonus points!