Final answer:
The element with the electron configuration [Kr] 5s¹ is rubidium (Rb), which directly follows krypton on the periodic table and has an atomic number of 37.
Step-by-step explanation:
To identify the element with the electron configuration [Kr] 5s¹, start by considering the noble gas preceding the configuration, which in this case is krypton (Kr). The noble gas shorthand indicates that the element has all the electron configurations of krypton, plus additional electrons. Here, '5s¹' signals that one electron is in the 5s orbital, which is the next orbital to be filled after krypton's last orbital. This electron configuration belongs to the element that directly follows krypton in the periodic table, because it has one more electron than krypton.
Upon examining the periodic table, we find that krypton has an atomic number of 36, so the element with one additional electron would have an atomic number of 37. The element with atomic number 37 is rubidium (Rb), and hence, [Kr] 5s¹ is the electron configuration of rubidium.