What is the term for a specific arrangement of electrons in an atom's orbitals?

The term that describes the specific arrangement of electrons in an atom's orbitals is called "electron configuration." This concept refers to the distribution of electrons among the various energy levels and sublevels in an atom, which is crucial for understanding an element's chemical behavior and reactivity.

In an electron configuration, the arrangement is typically represented using the Aufbau principle, Hund's rule, and the Pauli exclusion principle, which collectively help determine how electrons fill up the atomic orbitals. By knowing the electron configuration of an atom, one can predict how it will participate in chemical bonding, interact with other elements, and influence its physical properties.

The other terms listed do not define this arrangement of electrons. For instance, electron affinity refers to the energy change associated with the addition of an electron to a neutral atom, nuclear charge denotes the total charge of the nucleus determined by the number of protons, and ionic radius refers to the size of an ion. None of these terms address the distribution of electrons in specific orbitals within an atom.