To determine which element has the electron configuration of [tex]\([ \text{Kr} ] 5s^2\)[/tex], let's analyze the electron configurations of each option provided.
1. Barium (Ba):
Barium is in Group 2 and Period 6 of the periodic table. Its electron configuration would be
[tex]\[
[ \text{Xe} ] 6s^2
\][/tex]
2. Calcium (Ca):
Calcium is in Group 2 and Period 4 of the periodic table. Its electron configuration would be
[tex]\[
[ \text{Ar} ] 4s^2
\][/tex]
3. Rubidium (Rb):
Rubidium is in Group 1 and Period 5 of the periodic table. Its electron configuration would be
[tex]\[
[ \text{Kr} ] 5s^1
\][/tex]
4. Strontium (Sr):
Strontium is in Group 2 and Period 5 of the periodic table. Its electron configuration would be
[tex]\[
[ \text{Kr} ] 5s^2
\][/tex]
Among these options, strontium (Sr) matches the given electron configuration [tex]\([ \text{Kr} ] 5s^2\)[/tex].
Thus, the element with the electron configuration [tex]\([ \text{Kr} ] 5s^2\)[/tex] is strontium.
