Final answer:
The species that have a pseudo-noble gas configuration are Br, Sr²+, Rb+, and O2-.
Step-by-step explanation:
A pseudo-noble gas configuration is when an atom or ion has the same electron configuration as a noble gas by gaining or losing electrons. The noble gases have a stable electron configuration with a full outer shell, which makes them very unreactive. To determine which of the given species have a pseudo-noble gas configuration, we need to compare their electron configurations to those of the noble gases.
The electron configuration of a neutral bromine atom (Br) is [Ar] 4s² 3d¹⁰ 4p⁵. It is one electron away from having a full outer shell like the noble gas krypton (Kr). When Br gains one electron, it forms the Br- ion with an electron configuration of [Kr]. Therefore, option A) Br has a pseudo-noble gas configuration.
The electron configuration of a Sr²+ ion is [Kr]. It has the same electron configuration as the noble gas krypton, so Sr²+ also has a pseudo-noble gas configuration. Therefore, option B) Sr²+ has a pseudo-noble gas configuration.
The electron configuration of a Rb+ ion is [Kr]. It also has the same electron configuration as krypton, so Rb+ has a pseudo-noble gas configuration. Therefore, option C) Rb+ has a pseudo-noble gas configuration.
The electron configuration of an O2- ion is 1s² 2s² 2p⁶. It has the same electron configuration as the noble gas neon, so O2- also has a pseudo-noble gas configuration. Therefore, option D) O2- has a pseudo-noble gas configuration.