The noble gas electron configuration for strontium (Sr) is [Kr] 5s2.
Here’s the explanation:
Strontium has an atomic number of 38, which means it has 38 electrons. To write its noble gas electron configuration, we start by identifying the nearest noble gas that comes before strontium in the periodic table. In this case, it’s krypton (Kr), which has an atomic number of 36.
Krypton’s electron configuration is [Kr], which accounts for the first 36 electrons. The remaining 2 electrons in strontium occupy the 5s orbital. Therefore, the noble gas electron configuration for strontium is written as [Kr] 5s2.