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

Answer : The correct option is Kr.

Explanation :

Element = Kr

Atomic number = 36

Electronic configuration of Kr is

As given in the question, the element had valence electron in a 5s sub-shell which means that before filling the 5s sub-shell, the electrons were filled in 4p orbital. The complete electronic configuration upto 4p is the noble gas configuration of Kr.

So, the symbol of 'Kr' will be included as the noble gas notation while writing the electronic configuration of an element which had valence electrons in the 5s sub-shell.