Explanation
Which among the following elements shown in the table forms amphoteric oxide?
Hint: In an aqueous solution,
$$ Ionic\ Radius\ \propto \ mobility$$
Step 1: Reason for the decrease in mobility
Consider mobility of ions in an aqueous solution.
Step 2: Trend in mobility along the group:
Hence, the correct answer is option $$D.$$
Hint: $$ \uparrow Ease\ of\ emission\ of\ e^{-} = \uparrow$$ Photoelectric effect
Correct Answer: Option A
Photoelectric effects involve the emission of electrons from the metal surface due to the incidence of light radiations.
Electrons are easily knocked out of atoms when ionization energy $$(I.E.)$$ is low.
$$I.E.$$ is low when there is high shielding and low effective nuclear charge. Therefore, $$I.E.$$ decreases down the group.
Thus, the order of ease of emission of an $$e^-$$ is $$ Cs> K> Na> Li$$.
Hint: $$Li^{+}$$ has high polarizing power.
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