Neet Solved Paper 2015 Question 2
Question: The species $ Ar,{K^{+}} $ and $ C{a^{2+}} $ contain the same number of electrons. In which order do their radii increase?
Options:
A) $ Ar+{K^{+}}<C{a^{2+}} $
B) $ C{a^{2+}}<Ar<{K^{+}} $
C) $ C{a^{2+}}<{K^{+}}<Ar $
D) $ {K^{+}}<Ar<C{a^{2+}} $
Show Answer
Answer:
Correct Answer: C
Solution:
- $ C{a^{2+}},<{K^{+}},<Ar $ $ Ar,{K^{+}} $ and $ C{a^{2+}} $ are isoelectronic i.e. with same number of electrons, 18. For isoelectronic species ionic radii decreases with increase in effective (relative) positive charge. Also $ Ar,,K $ and $ Ca $ belong to the same period (3rd period).
