Valence electrons Transitional Reasoning Practice

Questions

1. 1.

   A chemistry student analyzes the ground-state electron configuration of a neutral selenium atom ($Z = 34$), written as $1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^4$, to determine the number of electrons available in its outermost shell. The student notes that electrons occupy orbitals across four principal energy levels, including completely filled subshells. Based on the definition of valence electrons for main-group elements, which statement correctly identifies and justifies the number of valence electrons in a neutral selenium atom?

   • A) It has 6 valence electrons because only the electrons in the highest principal energy level ($n = 4$), namely $4s^2$ and $4p^4$, reside in the outermost shell.
   • B) It has 16 valence electrons because all electrons written after the noble gas core of argon, including $4s^2$, $3d^{10}$, and $4p^4$, act as valence electrons.
   • C) It has 4 valence electrons because only electrons residing in the partially filled $4p$ subshell are available to behave as valence electrons.
   • D) It has 14 valence electrons because the completely filled $3d^{10}$ subshell combines directly with the $4p^4$ electrons while the $4s^2$ electrons are shielded.

Answers and step-by-step solutions appear after you finish the test.