Final answer:
Chlorine (Cl) could not have the electron configuration of [Kr] because even when it gains an electron to become Cl⁻, its electron configuration corresponds to that of argon ([Ne] 3s² 3p⁶), not krypton.
Step-by-step explanation:
The student asked for identification of the atomic or ionic species that could not have the abbreviated electron configuration [Kr], which is shorthand for the noble gas krypton. Since krypton is a noble gas, its ground state, neutral atom itself would have this configuration. To answer this, we must consider the electron configurations of various elements and compare them to [Kr].
Potassium (K) has an electron configuration that can be abbreviated as [Ar] 4s¹, where [Ar] represents the electron configuration till argon. Because K can lose an electron to form the K⁺ ion, the electron configuration of K⁺ would then be [Ar], the same as argon, thus not [Kr].
Krypton (Kr) has an electron configuration of [Kr] because that is the noble gas configuration for krypton itself.
Calcium (Ca) has an electron configuration that can be abbreviated as [Ar] 4s². If it loses two electrons to form Ca²⁺, the electron configuration would be [Ar], similar to potassium losing one electron.
Chlorine (Cl) has an electron configuration of [Ne] 3s² 3p⁵. It tends to gain an electron to achieve a noble gas configuration, resulting in Cl⁻ with the electron configuration [Ne] 3s² 3p⁶, which corresponds to the argon configuration, not [Kr].
Therefore, the atom or ion that could not have the electron configuration of [Kr] is chlorine (Cl), as it does not have enough electrons to reach the electron configuration of krypton, even as an anion.