# What element is represented [Kr]5s^1?

Well if it's a neutral element, the element is $\text{rubidium.}$
In practice, we don't even have to know about electronic configuration. $K r$ has $Z = 36$; add an electron, and a nuclear proton (and possibly a few more neutrons), we get $Z = 37$, the $\text{atomic number}$ of $\text{rubidium}$. $\text{Claro?}$