Pirate Chemistry
Ionic Charges and Octet Rule
Sodium chloride isn’t the only ionic compound, though. There are thousands of different possible combinations of ions. How do we sort them all out? Once again, we can rely on the periodic table to help.
Let’s re-examine what happened with sodium. Sodium had 11 electrons but wanted to only
have 10; one of our stable numbers.
11
Na
23.0
Protons
Electrons Charge
Sodium Atom
11
11
0
Unstable;
incorrect electrons
Sodium Ion
11
10
+1
Stable;
correct electrons
http://www.colorado.edu/
physics/2000/periodic_table/
images/periodicAlkali.jpg
Let’s look at the other atoms in Sodium’s
family. These are lithium, potassium, rubidium, cesium and francium. None of
these atoms have a stable number of electrons (2, 10, 18, 36, 54, 86). However,
each of them is only 1 electron away from
being stable. Lithium with 3 is almost at 2.
Potassium at 19 is almost at 18 and so
forth.
3
Li
6.9
19
K
39.1
37
Rb
85.5
55
Cs
132.9
Protons
Electrons Charge
Lithium atom
3
3
0
Unstable;
incorrect electrons
Lithium ion
3
2
+1
Stable;
correct electrons
Potassium atom 19
19
0
Unstable;
incorrect electrons
Potassium ion
19
18
+1
Stable;
correct electrons
Rubidium
Atom
37
37
0
Unstable;
incorrect electrons
Rubidium ion
37
36
+1
Stable;
correct electrons
Cesium Atom
55
55
0
Unstable;
incorrect electrons
Cesium ion
55
54
+1
Stable;
correct electrons
All text copyright Chris Smith 2009. All pictures obtained from internet and are copyright of their owners but assumed to be public accessible. If you are the owner of a picture and want it removed, email csmith@d211.org, and
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Pirate Chemistry
Did you notice that each of the atoms on the previous page wanted to lose one electron and thus
went to a +1 charge? This is why they all are in the same column. They are part of the same
group or family; they share similar properties. Even though they have very different numbers
of electrons, all of them have only 1 electron in their valence shell– the outermost shell. This
is also why they are put into column 1 on the periodic table. Their placement there means they
have many electrons but only one of any consequence, it’s valence electron.
Li
http://www.learner.org/interactives/periodic/images/alkalimetals_new.gif
Na
K
Each of these elements
has one valence electron.
Rb
Cs
Fr
Alkali metals all react vigorously
in water. The pictures below show
Lithium, Sodium, Potassium, and
Rubidium all exploding in water.
Notice the different colors of each.
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sumed to be public
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9AC900584888F2DEEC768ED688B634
Pirate Chemistry
Instead of looking at the alkali metals like sodium, let’s examine the halogens with chlorine.
17
Cl
35.5
Protons
Electrons Charge
Chlorine Atom 17
17
0
Unstable;
incorrect electrons
Chloride Ion
18
-1
Stable;
correct electrons
17
http://www.chem4kids.com/
files/art/elem_halogen1.gif
Let’s look at the other atoms in Chlorine’s family. These
are Fluorine, Bromine, and Iodine None of these atoms
have a stable number of electrons (2, 10, 18, 36, 54, 86).
However, each of them is only 1 electron away from being
stable. Fluorine with 9 is almost 10, Bromine with 35 is
almost 36, Iodine with 53 is almost 54, and so forth.
9
F
19.0
35
Br
79.9
53
I
126.9
Protons
Electrons Charge
Fluorine atom
9
9
0
Unstable;
incorrect electrons
Fluoride ion
9
10
-1
Stable;
correct electrons
Bromine atom
35
35
0
Unstable;
incorrect electrons
Bromide ion
35
36
-1
Stable;
correct electrons
Iodine atom
53
53
0
Unstable;
incorrect electrons
Iodide ion
53
54
-1
Stable;
correct electrons
Fluorine has 2 electrons in the first shell and then 7 in the outer shell.
Chlorine has 2 in the first shell, 7 in the next, and 7 in its outer shell.
Continuing the trend we saw from the alkali metals, all of the Halogens must have 7 electrons in their outer shells and each of them
needs only 1 more to make it complete. This is why Halogens are in
group 7 on the periodic table. By gaining one more electron the
Halogens all go to a –1 charge.
F
Cl
Br
I
At
http://upload.wikimedia.org/wikipedia/
commons/thumb/9/96/
Electron_shell_017_Chlorine.svg/558pxElectron_shell_017_Chlorine.svg.png
http://www.thenakedscientists.com/HTML/
uploads/RTEmagicC_558pxElectron_shell_009_Fluorine.svg.png.png
All the Halogens have 7
valence electrons which is
why they are in group 7 on
the Periodic Table.
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Pirate Chemistry
http://homepages.ius.edu/
DSPURLOC/c121/images/lewdot.gif
By using the idea of valence electrons, something that is complicated on the surface becomes
quite easy. We don’t have to look at ALL the electrons that an atom has, we only need to look
at the electrons past the preceding Noble Gas; the valence electrons. If we keep to this trend we
see the following results:
Notice how in group 1 the element has 1 valence electron. In group 2, the element has 2 valence electrons. This continues across the period until we reach 8 valence electrons in group 8.
This leads us to a general rule that chemists use to determine the stability of atoms, the octet
rule. The octet rule says that most atoms will be stable when they have 8 valence electrons or
reach a noble gas configuration. Knowing all of this information and applying the idea of the
octet rule we can extrapolate out the charges that atoms go to.
Charges
+1
0
+2
+3
+/-4
-3 -2 -1
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Pirate Chemistry
We can see from the chart on the preceding page that metals, atoms to the left of the stair-step
line, tend to go to positive charges. Non-metals, atoms to the right of the stair-step tend to go
to negative charges. An ionic compound needs one of each of these to form.
Example 1:
Calcium
Example 2:
Oxygen
20 electrons (unstable number)
2 in the first shell
8 in the second shell
8 in the third shell
2 in the fourth (valence) shell
8 electrons (unstable number)
2 in the first shell
6 in the second (valence) shell
Calcium will lose 2 electrons in valence shell
Oxide ion:
10 electrons (stable number)
2 in the first shell
8 in the second shell (octet rule satisfied)
Calcium ion:
18 electrons (stable number)
2 in the first shell
8 in the second shell
8 in the third shell (octet rule satisfied)
Oxygen will gain 2 electrons in valence shell
2, 8
Oxide ion
-2
http://upload.wikimedia.org/wikipedia/
commons/thumb/0/09/
Electron_shell_008_Oxygen.svg/150pxElectron_shell_008_Oxygen.svg.png
https://cornellchem.wikispaces.com/file/view/
Electron_shell_020_calcium.png/47421581
Example 3:
http://www.bbc.co.uk/schools/gcsebitesize/
science/images/diag_calcium_2.gif
Aluminum
Example 4:
13 electrons (unstable number)
2 in the first shell
8 in the second shell
3 in the third (valence) shell
Nitrogen
7 electrons (unstable number)
2 in the first shell
5 in the second (valence) shell
Nitrogen will gain 3 electrons in valence shell
Aluminum will lose 3 electrons in valence shell
Aluminum ion:
10 electrons (stable number)
2 in the first shell
8 in the second shell (octet rule satisfied)
Aluminum ion
Nitride ion:
10 electrons (stable number)
2 in the first shell
8 in the second shell (octet rule satisfied)
Nitride ion
2, 8
2, 8
-3
+3
http://upload.wikimedia.org/wikipedia/
commons/thumb/4/41/
Electron_shell_013_Aluminium.svg/558pxElectron_shell_013_Aluminium.svg.png
http://creationwiki.org/pool/images/thumb/a/
ab/Electron_shell_Nitrogen.png/150pxElectron_shell_Nitrogen.png
All text copyright Chris Smith 2009. All pictures obtained from internet and are copyright of their owners but assumed to be public accessible. If you are the owner of a picture and want it removed, email csmith@d211.org, and
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Pirate Chemistry
1. How many valence electrons does each of the following atoms have?
A. Potassium, K
B. Sulfur, S
C. Phosphorous, P
D. Neon, Ne
E. Aluminum, Al
F. Boron, B
G. Fluorine, F
H. Carbon, C
I. Magnesium, Mg
J. Sodium Na
2. What charge do each of
these atoms go to when
they become stable ions? Charge +1
A. Potassium, K
+2
+3 +/-4
B. Sulfur, S
C. Phosphorous, P
D. Neon, Ne
E. Aluminum, Al
F. Boron, B
G. Fluorine, F
H. Carbon, C
I. Magnesium, Mg
J. Sodium Na
3.
4.
5.
6.
http://homepages.ius.edu/
Questions
0
-3
-2
-1
What are the stable numbers of electrons?
What is the octet rule?
What charges do metals tend to go to, positive or negative?
What charges do non-metals tend to go to, positive or negative?
All text copyright Chris Smith 2009. All pictures obtained from internet and are copyright of their owners but assumed to be public accessible. If you are the owner of a picture and want it removed, email csmith@d211.org, and
it will be.