An atom has an 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 (7), F (9), P (15), Ar (18)

AcademicChemistryNCERTClass 10

(a) An atom has an electronic configuration 2, 8, 7. Hence, its atomic number is 2+8+7=17. Chlorine has the atomic number 17.

(b) Chlorine is similar to fluorine, F (9), the electronic configuration will be 2,7. Both chlorine and fluorine have 7 electrons in their outer shell, hence they are similar.

[Extra information: 

Periodic table: A periodic table is a tabular display of all the chemical elements that are arranged by the order of their atomic number, electronic configuration, and recurring chemical properties. 

It displays the names, atomic numbers, symbols and atomic weights of known elements. It serves as a great tool for solving chemistry problems.

The periodic table is important because it is organized to provide a great deal of information about elements and how they relate to one another in one reference. The table can be used to predict the properties of all the elements, even those that have not yet been discovered.]

Updated on 10-Oct-2022 13:19:17