Question

Which of the following represents the correct increasing order of first ionization enthalpy for Ca, Ba, S, Se and Ar?

• A. Ca < S < Ba < Se < Ar
• B. Ar < S < Ba < Se < Ca
• C. Ba < Ca < Se < S < Ar
• D. Ba < Ca < S < Se < Ar
• E. Ca < S < Ar < Se < Ba

Hint:

Chemistry Tip: Down a group ionization enthalpy decreases because outer electron is farther from nucleus and more shielded.

Answer 1

The Correct Option is C

Concept:
First ionization enthalpy generally: - Increases across a period (left to right) - Decreases down a group Noble gases have very high values due to stable configuration.
Step 1: Compare Ba and Ca (same group 2).
Ba lies below Ca in group 2, so it has larger size and lower ionization enthalpy. $$\text{Ba}<\text{Ca}$$
Step 2: Compare Se and S (same group 16).
Se lies below S, so: $$\text{Se}<\text{S}$$
Step 3: Argon as noble gas.
Argon has complete octet, so highest among given elements.
Step 4: Combine all comparisons.
Thus increasing order: $$\text{Ba}<\text{Ca}<\text{Se}<\text{S}<\text{Ar}$$ Hence correct option is (C). :contentReference[oaicite:0]{index=0}