<span>D. It shows that the electrons within an atom do not have sharp boundaries.</span>
Answer:
C. The lowest-energy electron configuration of an atom has the maximum number of unpaired electrons, all of which have the same spin, in degenerate orbitals.
Explanation:
The Hund's rule is used to place the electrons in the orbitals is it states that:
1. Every orbital in a sublevel is singly occupied before any orbital is doubly occupied;
2. All of the electrons in singly occupied orbitals have the same spin.
So, the electrons first seek to fill the orbitals with the same energy (degenerate orbitals) before paring with electrons in a half-filled orbital. Orbitals doubly occupied have greater energy, so the lowest-energy electron configuration of an atom has the maximum number of unpaired electrons, and for the second statement, they have the same spin.
The other alternatives are correct, but they're not observed by the Hund's rule.
Chromium has the electron configuration [Ar]4s13d5 and exhibits oxidation numbers 2+, 3+, and 6+. When chromium loses two electrons, it forms the Cr2+ ion and has the configuration [Ar]3d4.
The Answer is B. [Ar]3d4
