The Periodic Table
Objectives: write electron configurations for neutral atoms AND ions, recognize ALL
connections between the periodic table and electron configurations, recognize ALL stable
electron configurations, and determine the most probable ion that ALL atoms will form
(valence number)
Leading Question: What does the A on top of some columns of the Periodic Table mean?
Element
Al
Na
1s22s22p63s23p1
# electrons in highest
energy level
3
1s22s22p63s1
1s22s22p5
1
7
Electron Configuration
number in
front of A
3
1
F
7
Answer the leading question above in a complete and thorough sentence: The number
of electrons in the highest energy level can be found by looking at the
number in front of A at the top of the column.
Predict how many electrons are in the highest energy level of Carbon (C) : 4
Leading Question: What does the B on top of some columns of the Periodic Table mean?
Element
Fe
Ni
Zn
Electron Configuration
1s22s22p63s23p64s23d6
# electrons in the
highest energy
level
2
1s22s22p63s23p64s23d8
1s22s22p63s23p64s23d10
2
2
Answer the leading question above in a complete and thorough sentence:
The number of electrons in the highest energy level for the elements in
columns with a B is 2 unless the element displays the s1 exceptions
discussed in class.
Predict how many electrons are in the highest energy level of Cadmium (Cd): 2
How does electron configuration predict valence number?
T. O’Toole
electron dot diagram: express the number of electrons in the highest energy level as a
number of dots around the element symbol, putting no more than 2 electrons on a side.
Predict the electron dot diagram of Nitrogen (N)
Predict the electron dot diagram of Cobalt (Co)
Predict the electron dot diagram of Barium (Ba)
Leading Question: How do you determine the valence number of an element?
valence number: the smallest number of electrons that is either gained or lost so that the
electron configuration has s2p6 in the highest energy level
Element
1s22s22p63s23p6
Ar
1s22s22p63s1
Na
F
1s22s22p5
Fe
2
2
6
2
6
Electron Configuration
valence number
0
+1
-1
2
6
1s 2s 2p 3s 3p 4s 3d
+2
In a complete sentence, explain how you will know if a valence number is negative?
A valence number will be negative if the element needs to gain 4 or fewer
electrons to have s2p6 in its highest energy level.
Answer the leading question above in a complete and thorough sentence:
If an element loses 4 or fewer electrons, it will have a + valence number. If an element gains
4 or fewer electrons, it will have a – valence number. Group 2A = +2. Group 6A = -2.
Predict the valence number of Nitrogen (N) 5A therefore -3
Predict the valence number of Cobalt (Co) 2 electrons in highest energy level
therefore +2
Predict the valence number of Barium (Ba) 2A therefore +2
Explain the relationship that exists between an element’s electron dot diagram and its
corresponding valence number:
Valence number is + number of dots for 1-4. Valence number is dots -8
for 5-8.
How does electron configuration predict valence number?
T. O’Toole
WRAP UP:
1. The valence number of all elements in group 3A is: +3
2. The valence number of all elements in group 6A is: -2
3. The valence number of Nickel and the other elements filling the “d” shape is: +2
4. Are there more elements with positive valence numbers or negative valence numbers?
Positive valence numbers
Extra Practice: “Cracking the Periodic Table Code” PPT file on the website, read pages 413418, http://www.quia.com/jg/1263758.html, and
http://antoine.frostburg.edu/chem/senese/101/bonds/faq/valence-vs-valenceelectrons.shtml,
How does electron configuration predict valence number?
T. O’Toole