Question

5. Identify and explain the trend in atomic size (radius), in terms of atomic structure, for the following transitions in the periodic table. (a) Moving vertically from Ar to He (b) Moving horizontally from Na to Ar

Answer 1

18 He @ moving vertically from Ar to He If we see periodic table from Helium to Me Neon and upto Ar atomic size and radius Ar increases due to one new shell added to the outermust part of the atom. Hence size increases from top to bottom and size decreases from Ar to Helium due to reduction of one shell. 6 moving horizontally from Na to Ar Nas Av moving Ma to Ar atomic size decreases reason is attraction between nucleus and electrons. If we go from left to right number of protons and electrons increases. Hence attraction between them is also increases. Hence size and radius decrease from Na Ar