Question

Arrange the following metals in the order of increasing work function
(A) Potassium (K)
(B) Cesium (Cs)
(C) Platinum (Pt)
(D) Calcium (Ca)
Choose the correct answer from the options given below:

• A. (A), (B), (C), (D).
• B. (B), (A), (D), (C).
• C. (B), (A), (C), (D).
• D. (C), (D), (A), (B).

Hint:

Work function increases with metal’s ionization energy and decreases with atomic size. Alkali metals have the lowest work functions.

Answer 1

The Correct Option is C

Step 1: Recall work function.
The work function (\(\phi\)) is the minimum energy needed to remove an electron from the surface of a metal. It depends on the metal’s electron affinity. Metals with a low ionization energy have a low work function, while metals with higher ionization energies have higher work functions.
Step 2: Compare the metals.
- Cesium (Cs) has the lowest work function due to its low ionization energy (alkali metal).
- Potassium (K) also has a low work function, but higher than Cs.
- Calcium (Ca) is an alkaline earth metal and has a higher work function than alkali metals.
- Platinum (Pt), a noble metal, has the highest work function due to its stable, tightly bound electrons.
Step 3: Conclusion.
Thus, the order of increasing work function is: \[ \text{Cs}<\text{K}<\text{Ca}<\text{Pt} \]
Final Answer: \[ \boxed{\text{(B), (A), (C), (D)}} \]