Final answer:
The gas-phase ion with the largest number of unpaired electrons in its ground state would be based on an element's electron configuration and Hund's rule. Nitrogen, for example, would have three unpaired electrons in the 2p orbitals.
Step-by-step explanation:
The question refers to the number of unpaired electrons in the ground state of gas-phase ions, which is a topic related to atomic structure and electron configuration in chemistry. In general, elements with a higher nuclear charge tend to have electrons more closely bound to the nucleus due to the increase in electrostatic attraction, which affects the size of the ions and their properties such as ionization energy and electron affinity. To find out which ion has the most unpaired electrons, one must consider the electron configurations of the ions. For example, a nitrogen atom (atomic number 7) will have three unpaired electrons in its p orbitals following Hund's rule, as it fills the 1s, 2s and has one electron in each of the three 2p orbitals. Oxygen (atomic number 8) and fluorine (atomic number 9) will have fewer unpaired electrons because they start to pair up in the 2p orbitals. Noble gases like neon (atomic number 10), with all electrons paired, will not have any unpaired electrons in a neutral state. However, other factors need to be considered when ions are in the gas phase, particularly the formation of ions like oxide (O²-), which is energetically unfavorable in the gas phase, and discussing anomalies in ionization energies between elements of different groups.