Question

Figure 5-1 shows a portion of a blank periodic table. Identify the segments labeled A and B.

A. A and B are both periods.

B. A is a period and B is a group.

C. A and B are both groups.

D. A is a group and B is a period.

Answer 1

the groups are in the columns and the periods in the rows

Periods

Rows of elements are called periods. The period number of an element signifies the highest unexcited energy level for an electron in that element.
The number of elements in a period increases as you move down the periodic table because there are more sublevels per level as the energy level of the atom increases.

Groups

Columns of elements help define element groups. Elements within a group share several common properties. Groups are elements have the same outer electron arrangement. The outer electrons are called valence electrons. Because they have the same number of valence electrons, elements in a group share similar chemical properties. The Roman numerals listed above each group are the usual number of valence electrons. For example, a group VA element will have 5 valence electrons.

http://chemistry.about.com/od/k12gradelessons/a/periodictable_2.htm