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Beginning students of chemistry often think of the science as a mere collection of
disconnected data to be memorized by brute force. Not at all! Just look at it
properly and everything hangs together and makes sense. —Isaac Asimov (1920–
1992)
Periodic property: one that is predictable based on an element’s position within the
periodic table.
1. Use your periodic table and complete table below.
Element Nuclear
Abbreviated electron
#inner core
Charge
configuration
electrons
(shielding
electrons)
#Valence
Electrons
Effective
nuclear
charge
(Nuclear
charge-inner
core)
Na
Si
S
Ar
B
Al
Ga
In
Use complete sentences whenever you are asked to explain.
2. What is nuclear charge?
3. Explain electron shielding.
4. Explain effective nuclear charge.
5. Explain the attractive force of the nucleus and electrons and the repulsive forces of the
electrons. Think about how these forces play a role in atomic radius and ionization
energy.
6. Compare electron shielding through a period to moving down a family. Explain fully.
Use an analogy or metaphor to illustrate your understanding of electron shielding.
7. On the basis of their positions in the periodic table, select the atom
with the larger atomic radius in each of the pairs below and explain why the atom chosen
has a larger atomic radius:
a. K and Fr
b. Mg and P
c. C and Ne
d. Ar and Rn
8. Explain fully and in your own words the octet rule. Provide examples of how this rule
is applied using the elements K, Mg, Al, P, S, Br, He, Ar. Provide a picture for each
example of an atom with electron configuration. (use a separate piece of paper)
9. Compare the neutral atom to the ion of the same element for the following elements,
Na, Ga, N, and F. Draw the atom (protons, neutrons, and electrons) and ion including
electron configuration labeled in the energy levels. Provide the atomic symbol for all.
During the formation of an ion what happens to the size of the atomic radius and why? Explain fully. (use a separate piece of paper) 10. The most chemically reactive metal elements are soft metals with relatively low
melting points. These metals are so reactive that they react spontaneously with water
and/or substances in the atmosphere and therefore must be stored under oil. Where is this
family of metals located in the periodic table? Using the periodic trends explain why
these metals are so reactive.
11. You have investigated periodic table trends utilizing applets, graphs, and laboratory
exercises, use the knowledge gained from these investigations and formulate and record a
hypothesis regarding the comparative reactivity of the halogens, alkaline earth metals,
and alkali metals.
12. Which statement is true? Explain your choice.
(a) An orbital that penetrates into the region occupied by core electrons is more
shielded from nuclear charge than an orbital that does not penetrate and will therefore
have a higher energy.
(b) An orbital that penetrates into the region occupied by core electrons is less
shielded from nuclear charge than an orbital that does not penetrate and will therefore
have a higher energy.
(c) An orbital that penetrates into the region occupied by core electrons is less
shielded from nuclear charge than an orbital that does not penetrate and will therefore
have a lower energy.
(d) An orbital that penetrates into the region occupied by core electrons is more
shielded from nuclear charge than an orbital that does not penetrate and will therefore
have a lower energy.
13. Which statement is true about electron shielding of nuclear charge? Explain your
choice.
a) Outermost electrons efficiently shield one another from nuclear charge.
b) Core electrons efficiently shield one another from nuclear charge.
c) Outermost electrons efficiently shield core electrons from nuclear charge.
d) Core electrons efficiently shield outermost electrons from nuclear charge.
14. Which statement is true about effective nuclear charge? Explain your choice.
a) Effective nuclear charge increases as you move to the right across a row in the
periodic table and increases as you move down a column.
b) Effective nuclear charge increases as you move to the right across a row in the
periodic table and decreases as you move down a column.
15. Bromine, a non-metal, is highly reactive liquid while krypton is an inert gas. Explain
the difference based on their electron configurations and periodic trends.
http://www.youtube.com/watch?v=t4tejJk4TDM
16. Potassium is a highly reactive metal while argon is an inert gas. Explain the
difference based on their electron configurations and periodic trends.
http://www.youtube.com/watch?v=ewIA0N8wX18
17. Explain why vanadium(radius = 134 pm) and copper (radius = 128 pm) have nearly
identical atomic radii, even though the atomic number of copper is about 25% higher than
that of vanadium. What would you predict about the relative densities of these two
metals? Look up the densities on the ptable.com. What is the trend in density as you
move down a family? What is the trend in density as you move through a period from left
to right?
18. Examination of the first few successive ionization energies for a given element
usually reveals a large jump between two ionization energies. For example, the
successive ionization energies of magnesium show a large jump between IE 2 and IE 3.
The successive ionization energies of aluminum show a large jump between IE 3 and IE
Explain why these jumps occur and how you might predict the jumps for the main group
elements. Use ptable.com to analyze ionization energy data for an element.
19. We have seen how the number of electrons and the number of protons affects the size of an atom or ion. However, we have not considered how the number of neutrons affects the size of an atom. Why not? Would you expect isotopes—for example, C-­‐1 2 and C-­‐1 3—to have different atomic radii? 20. Exceptions to Trends in First Ionization Energy If we carefully examine period 2, we can see some exceptions to the trends in first ionization energies. For example, boron has a smaller ionization energy than beryllium, even though it lies to the right of beryllium in the same row. Explain what causes this exception. 21. Another exception occurs between nitrogen and oxygen. Although oxygen is to the right of nitrogen in the same row, it has a lower ionization energy, Examine the electron configurations and orbital diagrams of nitrogen and oxygen and explain why oxygen has a lower IE than nitrogen. 22. Explain and discuss the following:
What element is the most reactive metal on the PT and why?
What element is the most reactive non-metal on the PT and why?
What element is the most unreactive element on the PT and why?