# Chapter 8 - Sections 8.1-8.9 - Exercises - Problems by Topic: 49a

Vandium or Arsenic.

#### Work Step by Step

The electron configuration in the fourth period with five valance elctrons can either be $[Ar]4s^{2}3d^{3}$ or $[Ar]4s^{2}3d^{10}4p^{3}$, which corresponds to the elements vandium and arsenic.

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