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Chemistry
Extension: Electrons and the Periodic Table
The periodic table is the chemist’ s most basic and, perhaps, most useful
tool. We have seen that
the periodic table can be used to predict properties of the elements such as
boiling point, melting
point, and formation of oxides and chlorides, but its usefulness does not
end there.
An element’s reactivity can be determined by actually combining
it with a variety of other
substances. but this is not always practical or safe. Since an elemen
t’s reactivity is dependent
upon the electron arrangements in its atoms, knowing the electro
n arrangements is helpful
information in predicting reactivity. Specifically, the arrangement
or configuration of the
outermost or valence electrons is the most important information.
In this activity, you will determine the relationship between an element’s
position on the periodic
table and the element’s valence electron configuration. When
you have finished, you
should be able to predict an element’s electron structure and, therefore,
its reactivity based on the
periodic table alone.
The valance electron configuration is made up of three pieces of inform
ation which each receives
its own notation. The first piece of information is energy level or
shell, which is noted using
whole number integers (1,2,3...). Next are the sublevels represented
by one of four letter; s, p, ci,
f Finally, an exponent raised to the sublevel letter represents the numbers of electrons contain
ed
within a given number of orbitals found in that particular sublevel.
1
Example: Lithium (Li): I S
2
LS
1
From the example above, one could determine that an atom of the elemen
t Lithium has 2
electrons in the s-sublevel of the first energy level and 1 electron in the
s-sublevel of the second
energy level.
1. Based upon the definition for valence electrons given in the background
information, devise a
definition for valence shell.
2. Examine groups 1, 2 and 13-18 on the periodic table and identify two
patterns that can be
observed regarding the valence electrons and valence shells.
3. Using the patterns identified in question #2, predict the following information for the elements
indicated:
Cs
S
a. number corresponding to the valence shell
b. sublevel(s) which contain valence electrons
c. number of valence electrons
4. Examine the periods on the periodic table and identify two patterns that can be observed
regarding the valence electrons and valence shells.
5. Using the patterns identified in question #4, predict the following information for the elements
indicated:
Mg
Sn
a. number corresponding to the valence shell
b. sublevel(s) which contain valence electrons
c. number of valence electrons
6. Complete all empty squares on the periodic table using the same format and infonnation
provided for the other elements.
7. When elements react to form ionic compounds, the atoms either lose or gain electrons to form
ions with filled valence shells since this is the most stable electron structure. Based on your
determination of trends in electron structure on the periodic table, at the top of each group,
write the charge for the ions formed from atoms in groups 1, 2, 13, and 16-18.
s and it bonds with element Z
1p
2
2
3
3
4
6
8. If element X has an electron arrangement of 2
s what would the formula of the
2p
1s
2
3
6
3
2
,
which has an electron arrangement of 5
resulting compound be, in terms of X and Z? (Hint: Figure out the charge of elements X and Z
and then write the corresponding formula.)
9. Suggest why the metals in group 1 might be the most reactive metals.
+1
IsZ2si
+1
1
Is
+1
Fr
+1
[KrI5s’
+1
[RiiI7s’
Cs
÷i
[Arj4s’
Rb
K
—
I2
2
s
2
p3s’
s
Na
Li
[1
-
+2
2
[KrJ5s
+2
[Rn
Ra
751
+2
2
[XeJ(,s
Ba
Sr
+2
2
[ArJ4s
Ca
+2
2s
2
1s
Mg
Be
2
—
—
—
—
—
—
567
8
9
11
—
—
12
+
+3
+I+3
XJ6s
6
2
p’
TI
tKrj5s
5
t
p’
In
[Ar]4s
4
2
i
a
1
2
1s
2
3
6
3
2
p
s
+3
-4,+2,
+4
2p
1s
2
2
s
-4,+2,
+4
+2,+4
6p
2
[Xe]6s
Pb
Sn
4p
2
[Arj4s
GC÷
,
2
±4
2p
1s
2
3
6
3
2
s
Si
C
14
I
-3
-3
3
2
ls
2
2
p
s
15
-3
-
1
6
2
[Xej6s
p
Bi
3
5
2
rj5s
p
Sb
3
4
2
[ArJ4s
p
As
-2
-2
16
+2,+4
[Xejós
6
2
p’
Po
-2
1t\14s
4
2
l
S
S
0
Charges
3
2
1s
2
3
2
p”3s
p
s
P
IN
anJ
I
-i
]
6
2
p
At
[Kuj5s
5
2
p
-i
The numbers at the bottom of each square represent the electrons and the regions of space they occupy 1 he larger
numbers represent the energy level where electrons might be found, while the superscripts represent the number of
electrons in that particular energy level. The letter (s or p) represents the sublevel(s) in which the electrons are found.
—-
1s
0
Rn
Xc
o
0
[Aij4s
4
2
p
o
2p
1s
2
3
6
3
2
s
Ar
Ne
Ic
-iKr
[\J4s
4
2
p
Fr
1
-i
2p3s
2
s2s
3
p
Fl
2s22
F
17
The charge(s) for the ion(s) formed ilom atoms of each element are shown in the upper right corner of each square
Some elements have other possible charges in addition to those indicated.
10
+3
2
2
1s
2
p’
s
Al
B
13
Periodic Table with Electrons
18