Which of the following electronic configuration is/arecorrect?(i) 23Na 1s22s22P63s1(ii)29Cu [Ar] 4s13d10(iii)24Cr [Ar] 4s23d4
Correct answer: C. I and II only
- A. I only
- B. I and III only
- C. I and II only
- D. II and III only
Explanation
The electron configuration for sodium (23Na) is correctly given as 1s22s22p63s1. Copper (29Cu) also follows the expected pattern of [Ar] 3d10 4s1, which is an exception to the expected filling order due to the stability of a fully filled d sublevel. However, chromium (24Cr) is an exception that does not follow the typical filling order; its electron configuration is [Ar] 3d5 4s1 due to the stability associated with a half-filled d sublevel. Therefore, only statements I and II have correct configurations, making option C the correct choice.
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About Electronic Configuration
Electronic configuration describes how electrons occupy shells, subshells and orbitals around an atom. Questions use the Aufbau principle, Pauli exclusion principle and Hund's rule to write configurations, identify valence electrons, form ions and explain periodic trends, including common exceptions such as chromium and copper.
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