Chemistry Classification of Elements and Periodicity in Properties

Yield of 4-hydroxypentan-2-one is low because aldol and diacetone alcohol are also formed.

  $\Delta H_{eg}\left(M\right)=IE\left(M^{-}\right)$  

$M+e^{-}\underset{IE}{\overset{\Delta H_{eg}}{?}}{M}^{-}$            

Since sulphar has most -ve electron gain enthalpy hence S^- will have the highest IE.

The second ionization energy of K is maximum, because the second electron is removed from fully filled 3p? subshell. The second ionization energies of group 2 elements decrease down the group.
Hence, second I.E. of Ca > second I.E. of Ba.

Al < Mg < Si < S < P

1^st I. E increase along period with exception on moving from group 2 to group 13 and group 15 to group 16

Order of 1st I. E is Al < Mg < S < P

Correct order : Na? > Li? = Mg? > Be²?

Among isoelectronic monoatomic species, size is inversely proportional to atomic number. Hence among isoelectronic species Na? , O²? , N³? , F? (having the nearest noble gas configuration);
Order of size is Na? < F? < O? < N?
N³? has least atomic number hence the largest size

The difference between the first and second ionization energies is significantly higher for alkali metals (like Sodium, Na) compared to alkaline earth metals (like Magnesium, Mg). Therefore, in the context of the problem, X=Na and Y=Mg.

The atomic numbers and classifications for the given elements are: As (Arsenic, atomic no. 33) is a metalloid, I (Iodine, atomic no. 53) is a non-metal, and Bi (Bismuth, atomic no. 83) is a metal.

First ionization enthaly of Mg is smaller than Ar and Cl but higher than Na.