Observe the given table and question: answer the following
`{:("Elements", A, B, C, D, E),("Atomic number", 11,4,2,7,19):}`
Identify the two elements that belong to the same period and the two elements that belong to the same group. Give reason for your conclusion.

Explanation

The electronic configurations of the given elements are: A (11) = (2, 8, 1), B (4) =(2, 2), C (2) = (2), D (7) = (2,5), E (19) = (2, 8, 8, 1). B and D belong to same period since they have two shells each. A and E belong to same group since they have same number of valence electrons, i.e., I.