What is the electron configuration for potassium?

• (A) 1s² 2s² 2p⁶ 3s² 3p⁵
• (B) [Ar] 4s¹
• (C) 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁵
• (D) 3s² 4s² 4p¹

To determine the correct electron configuration for potassium, we first need to know its atomic number, which is 19. This means a neutral potassium atom has 19 electrons. The electron configuration describes how these electrons are distributed among the various atomic orbitals.

Breaking Down the Electron Configuration

Electrons fill orbitals in a specific order based on energy levels, following the Aufbau principle. The order of filling is generally as follows:

• 1s
• 2s
• 2p
• 3s
• 3p
• 4s
• 3d
• 4p

For potassium, we fill the orbitals in this order until we reach 19 electrons:

Step-by-Step Filling

1. **1s²**: The first two electrons fill the 1s orbital.

2. **2s²**: The next two electrons fill the 2s orbital.

3. **2p⁶**: The following six electrons fill the 2p orbital.

4. **3s²**: Two electrons fill the 3s orbital.

5. **3p⁶**: The next six electrons fill the 3p orbital.

6. **4s¹**: Finally, the last electron goes into the 4s orbital.

So, the complete electron configuration for potassium is:

Final Configuration

1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹

Comparing with the Options

Now, let’s look at the options provided:

• (A) 1s² 2s² 2p⁶ 3s² 3p⁵
• (B) [Ar] 4s¹
• (C) 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁵
• (D) 3s² 4s² 4p¹

Option (A) is incorrect because it has only five electrons in the 3p subshell instead of six. Option (B) is a shorthand notation that uses the noble gas configuration of argon ([Ar]) to represent the filled inner shells, followed by 4s¹, which is correct. Option (C) incorrectly adds extra electrons in the 4s and 3d orbitals. Lastly, option (D) misplaces the electrons in the 3s and 4p orbitals.

Correct Answer

The best choice that accurately represents the electron configuration for potassium is (B) [Ar] 4s¹. This notation is efficient and highlights the filled inner shells while indicating the valence electron in the 4s orbital.