The correct order of ionic radii for the ions, P3$$-$$, S2$$-$$, Ca2+, K+, Cl$$-$$ is :
A
P3$$-$$ > S2$$-$$ > Cl$$-$$ > K+ > Ca2+
B
Cl$$-$$ > S2$$-$$ > P3$$-$$ > Ca2+ > K+
C
P3$$-$$ > S2$$-$$ > Cl$$-$$ > Ca2+ > K+
D
K+ > Ca2+ > P3$$-$$ > S2$$-$$ > Cl$$-$$
Explanation
P3$$-$$ > S2$$-$$ > Cl$$-$$ > K+ > Ca2+ (Correct order of ionic radii)
all the given species are isoelectronic species. In isoelectronic species size increases with increase of negative charge and size decreases with increase in positive charge.
2
JEE Main 2021 (Online) 27th August Evening Shift
MCQ (Single Correct Answer)
Choose the correct statement from the following :
A
The standard enthalpy of formation for alkali metal bromides becomes less negative on descending the group.
B
The low solubility of CsI in water is due to its high lattice enthalpy.
C
Among the alkali metal halides, LiF is least soluble in water.
D
LiF has least negative standard enthalpy of formation among alkali metal fluorides.
Explanation
a. Standard enthalpy of formation for alkali metal bromides becomes more negative on descending down the group.
b. In case of CsI, lattice energy is less, but Cs+ is having less hydration enthalpy due to which it is less soluble in water.
c. For alkali metal fluorides, the solubility in water increases from lithium to caesium. LiF is least soluble in water.
d. Standard enthalpy of formation for LiF is most negative among alkali metal fluorides.
3
JEE Main 2021 (Online) 27th August Morning Shift
MCQ (Single Correct Answer)
In which one of the following molecules strongest back donation of an electron pair from halide to boron is expected?