Answer:
[Kr] 5s²
Step-by-step explanation:
Using the Aufbau principle, we can first write the electron configuration of strontium to then find its noble gas configuration. Note that the noble gas configuration is just a simpler, reduced method of the electron configuration.
Since we know strontium has an atomic number of 38, then we know it has 38 electrons. Remember that when writing electron configurations:
- s holds up to 2 electrons
- p holds up to 6 electrons
- d holds up to 10 electrons
Lets write the follow electron configuration:
1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p⁶5s²
Remember that the condensed noble gas configuration is just a shorter configuration for the noble gas elements with large atomic numbers. What you do is take the noble gas before strontium on the periodic table, which is Krypton, and put it in brackets with the last shell configuration of strontium (5s²). It should look like this:
[Kr] 5s²
Aufbau Principle: