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Periodic Trends

>> Parts of this equation/concept include:

A -	Periods and Groups
B -	Ionization Energy

Periods are rows of the periodic table, the topmost being period 1. The period corresponds to the highest n value in the electron configuration.

Groups are the columns of the periodic table. There are several different traditions for labeling these columns. The text uses the tradition of Roman numeral followed by a letter tradition. Groups have similar chemical properties. This is due to the same organization of the outermost electrons.

>> Example 1

What is the group and period of the following elements?

1. Re
2. Cu
3. Ca
4. Pb
5. Ga
6. Ce
7. F

Solution:

1. Group VIIB, period 6
2. Group IB, period 4
3. Group IIA, period 4
4. Group IVA, period 6
5. Group IIIA, period 4
6. Lanthanide, doesn't have a group number, period 6. (The lanthanide series is displaced from its proper position in the periodic table; however, if you look at the atomic numbers, you can see where it belongs.)
7. Group VIIA, period 2

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Ionization energy is the energy required to remove an electron from an atom in the gaseous state. Ionization energy increase from left to right across the periodic table, except for p⁴ atoms, which have slightly lower ionization energies than p³ atoms. Ionization energy also increases from bottom to top. You will not be asked to determine actual values for ionization energy; just do comparisons. Even then the trends are not sufficient to compare all atoms.

>> Example 1

Rank the following atoms from highest to lowest ionization energy.

F, S, He, Se, O

Solution:

He has the highest; it is a noble gas and at the top of the periodic table.

F is next at the right and in period 2.

O is next to F.

S is closer to the bottom but the same distance to the right as oxygen.

Se is below sulfur.

He > F > O > S > Se

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