The atomic number of elements A, B, C, D and E are given below
The atomic number of elements A, B, C, D and E are given below
| Element | A | B | C | D | E |
| Atomic no. | 7 | 10 | 12 | 4 | 19 |
From the above table, answer the following questions :
(i) Which two elements are chemically similar ?
(ii) Which is an inert gas ?
(iii) Which element belongs to 3rd period of periodic table ?
(iv) Which element among these is a non-metal ?
2 Answers
(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.