7.Modern Periodic table
Qno.1. Explain the following A. The elements Li, B, C, Be and N have the electronegativities 1.0, 2.0, 1.5 and 3.0, respectively on the Pauling scale. [2 Marks] Ans:- i. Li, B, Be and N belong to the same period. ii. As we move across a period from left to right in the periodic table, the effective nuclear charge increases steadily and therefore, electronegativity increases. Hence, the elements Li, B, Be and N have the electronegativities 1.0, 2.0, 1.5 and 3.0, respectively on the Pauling scale. B. The atomic radii of Cl, I and Br are 99, 133 and 114 pm, respectively. [2 Marks] Ans:- i. Cl, I and Br belong to group 17 (halogen group) in the periodic table. ii. As we move down the group from top to bottom in the periodic table, a new shell gets added in the atom of the elements. iii. As a result, the effective nuclear charge decreases due to increase in the atomic size as well as increased shielding effect. iv. Therefore, the valence electrons experie...