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:

number 36, which ends the 4th period). Kr's electron configuration is $[Ar] 3d^{10} 4s^2 4p^6$, so elements with 5s valence electrons use Kr as the noble gas core.

Answer:

number 36, which ends the 4th period). Kr's electron configuration is $[Ar] 3d^{10} 4s^2 4p^6$, so elements with 5s valence electrons use Kr as the noble gas core.