JEE MainChemistryPeriodic Table and PeriodicityMCQ+4 / −1
The ionic radii (in Å) of , and are respectively:
- A1.36, 1.71 and 1.40
- B1.71, 1.40 and 1.36
- C1.71, 1.36 and 1.40
- D1.36, 1.40 and 1.71
View written solutionFree
Correct answer: B
-
Identify the species
The ions are:
Each of these has 10 electrons, so they are isoelectronic with Ne.
-
Rule for isoelectronic species
In an isoelectronic series, ionic radius decreases as nuclear charge increases.
Here, the nuclear charges are:
- For :
- For :
- For :
Since all have the same number of electrons, the ion with the smallest nuclear charge holds the electron cloud least tightly and hence has the largest radius.
Therefore,
-
Match with given values
The three radii given are Å.
According to the order above:
- Largest radius 4ightarrow N^{3-} = 1.71\,\text{}
- Next 4ightarrow O^{2-} = 1.40\,\text{}
- Smallest 4ightarrow F^- = 1.36\,\text{}
-
Check options
- A: wrong
- B: correct
- C: wrong
- D: wrong
Hence, the correct option is B.
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