Classification Of Elements And Periodicity In Properties Ques 265
Question: The correct arrangement of decreasing order of atomic radius among Na, K, Mg and Rb is
Options:
A) Rb>Na>K>Mg
B) K>Rb>Na>Mg
C) Rb>K>Na>Mg
D) Mg>Rb>K>Na
Show Answer
Answer:
Correct Answer: C
Solution:
[c]Mg < Na < K < Rb. The order is based on the trend in a period and a group. The atomic radius decreases across a period (from left to right). The atomic radius increases down a group due to the addition of a new energy level. Mg lies on the right side of Na and so it is smaller in size than that of Na. K lies below Na in the same group and so, the size of K is greater than that of Na. And similarly, Rb is in the same group of K, Na and lies below K. Hence it has the largest size.
