An atom has electronic configuration 2, 8, 7. (a) What is the atomic number of this element ? (b) To which of the following elements would it be chemically similar? (Atomic numbers are given in parentheses.) N(71), F(9), P(15), Ar(18).

An atom has electronic configuration 2, 8, 7. (a) What is the atomic

1.	An atom has electronic configuration 2, 8, 7. (a) What is the atomic number of this element ? (b) To which of the following elements would it be chemically similar? (Atomic numbers are given in parentheses.) N(71), F(9), P(15), Ar(18).
Answer» Solution :Chlorine has the electronic CONFIGURATION 2, 8, 7. (a) Atomic number of an element is the sum of number of electrons or protons in the element. THEREFORE, atomic number of the element is `2 + 8 + 7 = 17`. (b) Chlorine is a halogen. Another halogen PRESENT in the group is F(9). Therefore, chlorine is chemically similar to F(9).