Question

Two elements A and B have the following configuration: $A:2,7;B:2,8,7$. Both of them belong to:

• A. the same group and are chemically similar
• B. different groups but are chemically similar
• C. the same group but are chemically dissimilar
• D. the same period and are chemically similar

Answer 1

The correct option is A the same group and are chemically similar

Electronic configuration shows both have $7$ valence electrons in the outermost shell. Similar chemical properties are related to the number of valence electrons and thus they belong to same group and have similar properties.