Question

Match the following: 

List-1 (Element)	List-2 (Block)
A: Cd	I: f-block
B: Eu	II: s-block
C: Se	III: d-block
D: Ba	IV: p-block

• A. A-IV, B-III, C-II, D-I
• B. A-II, B-IV, C-I, D-III
• C. A-III, B-IV, C-II, D-I
• D. A-III, B-I, C-IV, D-II

Hint:

The block of an element in the periodic table is determined by the subshell (s, p, d, or f) that receives the last electron according to the Aufbau principle. Knowing the general layout of the periodic table (s-block on the left, p-block on the right, d-block in the middle, f-block at the bottom) can help you quickly place many common elements.

Answer 1

The Correct Option is D

We need to determine which block of the periodic table each element belongs to based on its electron configuration.
A. Cd (Cadmium): The atomic number of Cd is 48. Its electron configuration is [Kr] \(4d^{10} 5s^2\). The last electron enters the d-orbital, so it belongs to the d-block. Thus, A matches with III.
B. Eu (Europium): The atomic number of Eu is 63. It is one of the Lanthanides. Its electron configuration is [Xe] \(4f^7 6s^2\). The differentiating electron enters the f-orbital, so it belongs to the f-block. Thus, B matches with I.
C. Se (Selenium): The atomic number of Se is 34. Its electron configuration is [Ar] \(3d^{10} 4s^2 4p^4\). The last electron enters the p-orbital, so it belongs to the p-block. Thus, C matches with IV.
D. Ba (Barium): The atomic number of Ba is 56. It is an alkaline earth metal. Its electron configuration is [Xe] \(6s^2\). The last electron enters the s-orbital, so it belongs to the s-block. Thus, D matches with II.
Combining these matches, we get: A-III, B-I, C-IV, D-II.