Question

which of the following symbols would be included in the noble gas notation for an element that had valence electrons in the 5s subshell?
○ ar
○ kr
○ xe
○ rn

Explanation:

To determine the noble gas for an element with valence electrons in the 5s subshell, we analyze the electron configurations of noble gases:

• Argon (Ar) has an electron configuration up to \(3p^6\), corresponding to the 3rd period. Elements with 5s valence electrons are in the 5th period, so Ar is too early.
• Krypton (Kr) has an electron configuration up to \(4p^6\). The next electrons fill the 5s subshell, so Kr is the noble gas that precedes elements with 5s valence electrons (as noble gas notation uses the noble gas from the previous period to represent core electrons).
• Xenon (Xe) has an electron configuration up to \(5p^6\), which is after the 5s subshell filling, so it's too late.
• Radon (Rn) is a heavier noble gas with a higher atomic number, also too late for 5s valence electrons.

Answer:

B. Kr