Question

Which electrons are higher in energy, 4s or 3d?

And specifically, which of the following possesses the highestenergy electron?

A) Br^-
B) Ca²⁺
C) Cr⁺
D) As

Br- --> [Kr] or[Ar]3d¹⁰4s²4p⁶
Ca²⁺ --> [Ar] or[Ne]3s²3p⁶
Cr⁺ --> [Ar]3d⁵
As --> [Ar]4s²3d¹⁰4p³

Could you tell me please why the correct answer is As with4p³
electrons, despite the fact that Br- has 4p⁶ electrons?Is it because
Br- has an electron configuration of a noble gas and thus haslower
electron energies in its outermost shell than As? If so, than ifwe
have a noble gas` electron configuration for any ion, can wedisregard
the rule that says that “electron energy level is determined bythe
first two quantum numbers (n and l)” ?