Final answer:
In the periodic table, a 'family' is a vertical column known as a group, containing elements with the same number of valence electrons and similar chemical properties.
Step-by-step explanation:
In the context of the periodic table, the term 'family' refers to a group, which is a vertical column of elements. Members of the same family have the same number of valence electrons, leading to similar chemical properties. For example, the alkali metals found in Group 1A are highly reactive and share certain chemical behaviors, such as forming compounds in the same ratios and with similar properties. Similarly, we have the alkaline earth metals in Group 2A, the halogens in Group 17 (or 7A), and the noble gases in Group 18 (or 8A).
Contrary to the options given in the question, families are neither rows (periods) nor specifically transition metals or noble gases alone. Transition metals span Groups 3 to 12, whereas noble gases are contained within the Group 18 family. The significance of families lies in their ability to predict the behavior of elements during chemical reactions due to their similar properties.