The atomic number of elements A, B, C, D and E are given below.
From the above table, answer the following questions.
(i) Which two elements are chemically similar?
(ii) Which element is an innert gas?
(iii) Which element belongs to 3rd period of periodic table?
(iv) Which element among these is a non-metal?
(i) C and D are the two elements which are chemically similar. This is because the electronic configuration of C is 2,8,2 and that of D is 2,2 , so both the elements contains same number of valence electrons.
(ii) Element B is an innert gas. This can be concluded by writing its electronic configuration as 2,8. Both the shells are completely filled. Thus it is an innert gas.
(iii) The element E belongs to the 3rd period. Its electronic configuration is 2,8,9 from which we can see that there are 3 shells present in it. So it belongs to 3rd period.
(iv) Element A is a non-metal. Its atomic number is 7, so its electronic configuration will be 2,5, we can see that it contains 5 valence electrons so it belongs to 15th group and will lie on the right side of the second period. On moving from left to right in a period, non-metallic character increases. Thus A is a non-metal.