To determine the correct noble gas configuration for Strontium (Sr), we need to confirm its position in the periodic table and identify its electron configuration accordingly.
1. Identify the Atomic Number of Sr:
- Strontium (Sr) has an atomic number of 38.
2. Understand Electron Configuration:
- The electron configuration of an element describes the distribution of electrons in the atomic orbitals.
- Using the Aufbau principle, which states that electrons occupy the lowest energy orbitals first, we can determine the electron configuration step by step.
3. Noble Gas Core Notation:
- To simplify the electron configuration notation, we use the nearest noble gas that comes before Sr in the periodic table as the core notation.
- The noble gas preceding Sr is Krypton (Kr), which has an atomic number of 36. Therefore, Krypton's electron configuration is: [tex]$[ Kr ]$[/tex].
4. Continuing Electron Configuration Beyond the Noble Gas:
- Starting from Kr, we need to add electrons to reach 38, which is the atomic number of Sr.
- After [tex]$[ Kr ]$[/tex], we next fill the 5s orbital.
5. Complete Electron Configuration for Sr:
- Since Kr covers 36 electrons, we need to place the remaining 2 electrons.
- The 5s orbital will be filled next: [tex]$5s^2$[/tex].
6. Correct Noble Gas Configuration:
- Therefore, the noble gas configuration of Sr is: [tex]$[ Kr ] 5s^2$[/tex].
Among the given choices:
A. [tex]$[ Kr ] 5 s^2$[/tex]
B. [tex]$[\operatorname{Ar}] 4 s^2$[/tex]
C. [tex]$[$[/tex] Ar] [tex]$] 5 s^2$[/tex]
D. [tex]$[K r] 4 s^2$[/tex]
The correct answer is:
A. [tex]$[ Kr ] 5 s^2$[/tex]
