Answer:
The answer is Kr (Krypton).
This is because krypton has an electronic configuration of:
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6
Taking note of the sequence of electronic configuration:
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s
It can be seen that Kyrpton's electronic configuration finishes just before the 5s subshell. Therefore, the noble gas notation for an element with valence electrons in the 5s subshell can use [Kr] as a shortcut to denote its electronic configuration. For example:
If an element has 1 valence electron in the 5s subshell, the noble gas notation will be:
[Kr] 5s1
Explanation:
