What is the correct simplified (noble-gas) electron configuration of krypton (Kr)?

• A. [Ne] $3^s$$2^{}$ $3^p$$6^{}$ $4^s$$2^{}$ $3^d$${10}^{}$ $4^p$$6^{}$
• B. [Ar] $4^s$$2^3$ $3^d$${10}^{}$ $4^p$$6^{}$
• C. [Ar] $4^s$$2^{}$ $3^d$${10}^{}$ $4^p$$6^{}$
• D. [Kr] $5^s$$2^{}$

Answer: (C)

Verified step by step guidance

1. Step 1: Identify the atomic number of krypton (Kr), which is 36. This means krypton has 36 electrons to arrange in its electron configuration.
2. Step 2: Recall the order of filling electron orbitals according to the Aufbau principle: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, and so on.
3. Step 3: Use the noble gas shorthand notation to simplify the configuration. Find the noble gas preceding krypton, which is argon (Ar) with atomic number 18. This allows you to start the configuration from [Ar].
4. Step 4: After [Ar], add the electrons that fill the 4s, 3d, and 4p orbitals to reach a total of 36 electrons. Specifically, fill 4s with 2 electrons, 3d with 10 electrons, and 4p with 6 electrons.
5. Step 5: Write the final simplified electron configuration as \([\mathrm{Ar}]\,4s^{2}\,3d^{10}\,4p^{6}\), which represents the full electron configuration of krypton using noble gas shorthand.