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: Understanding Work Function.
The work function (\(\phi\)) represents the minimum energy required to eject an electron from a metal's surface, influenced by the metal's electron affinity. Lower ionization energies correlate with lower work functions, and vice versa.
Step 2: Metal Comparison.
- Cesium (Cs) exhibits the lowest work function due to its minimal ionization energy as an alkali metal.
- Potassium (K) possesses a low work function, though higher than Cesium.
- Calcium (Ca), an alkaline earth metal, has a higher work function compared to alkali metals.
- Platinum (Pt), a noble metal, displays the highest work function because of its stable, strongly held electrons.
Step 3: Ordering by Work Function.
The increasing order of work function is: \[\text{Cs}<\text{K}<\text{Ca}<\text{Pt}\]
Final Answer: \[ \boxed{\text{(B), (A), (C), (D)}} \]