A. If an element with the valence configuration 4s¹3d⁵ loses 2 electrons, these electrons would be removed from the subshell 4s. This is because electrons are typically removed first from the outermost energy level (4 in this case) and then from the outermost subshell (4s).
B. An element with the valence electron configuration 5s²5p⁴ would form a monatomic ion with a charge of 2-. In order to form this ion, the element will gain 2 electrons into the subshell 5p. When elements gain electrons, they fill their valence shells or subshells to achieve a stable, full electron configuration. In this case, the element is gaining 2 electrons to complete the 5p subshell and achieve a stable electron configuration.