To determine which element has the electron configuration of [tex]\([ \text{Kr} ] \, 5s^2\)[/tex], let's break down the information given:
1. We're looking for an element that follows the noble gas krypton ([tex]\([\text{Kr}]\)[/tex]).
2. The configuration also specifies [tex]\(5s^2\)[/tex], indicating there are two electrons in the 5th shell's s orbital.
Now, let's review the electron configurations of the given options:
1. Barium (Ba):
- Atomic number: 56
- Electron configuration: [tex]\([ \text{Xe} ]\, 6s^2\)[/tex]
2. Calcium (Ca):
- Atomic number: 20
- Electron configuration: [tex]\([ \text{Ar} ]\, 4s^2\)[/tex]
3. Rubidium (Rb):
- Atomic number: 37
- Electron configuration: [tex]\([ \text{Kr} ]\, 5s^1\)[/tex]
4. Strontium (Sr):
- Atomic number: 38
- Electron configuration: [tex]\([ \text{Kr} ]\, 5s^2\)[/tex]
From the configurations above, Strontium (Sr) is the element that has the electron configuration [tex]\([ \text{Kr} ]\, 5s^2\)[/tex].
Thus, the element with the electron configuration [tex]\([ \text{Kr} ] \, 5s^2\)[/tex] is strontium.
