a. Arrange the following elements in descending order of their first ionization energies.
F
K
S
Ca
Si

b. Arrange the following in ascending order of their ionic radii.
O₂^-
N₃^-
Mg²⁺ 
F^-
K⁺

c. Arrange the following elements in descending order of their atomic radii.
Ca
K
F
Si
Ge
S

• A. a) F > S > Si > Ca > K; b) Mg²⁺ < F^- < O₂^- < K⁺ < N₃^-; c) K > Ca > Ge > Si > S > F
• B. a) K > Ca > Si > S > F; b) N₃^- < O₂^- < F^- < K⁺ < Mg²⁺; c) F > S > Si > Ge > Ca > K
• C. a) F > S > Si > Ca > K; b) N₃^- < O₂^- < F^- < K⁺ < Mg²⁺; c) K > Ca > Ge > Si > S > F
• D. a) K > Ca > Si > S > F; b) Mg²⁺ < K⁺ < F^- < O₂^- < N₃^-; c) F > S > Si > Ge > Ca > K

Answer: (A)