What is the ground-state electron configuration of potassium (K, atomic number 19)?

• A. $1s_{2}2s_{2}2p_{6}3s_{2}3p_{5}4s_2$
• B. $1s_{2}2s_{2}2p_{6}3s_{2}3p_{6}4s_1$
• C. $1s_{2}2s_{2}2p_{6}3s_{2}3p_{6}3d_1$
• D. $1s_{2}2s_{2}2p_{6}3s_{2}3p_6$

Answer: (B)

Verified step by step guidance

1. Identify the atomic number of potassium (K), which is 19. This means potassium has 19 electrons to arrange in its ground-state electron configuration.
2. Recall the order of filling electron orbitals based on the Aufbau principle: 1s, 2s, 2p, 3s, 3p, 4s, then 3d, and so on.
3. Start filling the orbitals with electrons following the order and the maximum number of electrons each subshell can hold: s can hold 2, p can hold 6, and d can hold 10 electrons.
4. Write the electron configuration by adding electrons to each subshell until you reach 19 electrons. This will include filling 1s, 2s, 2p, 3s, 3p completely, and then placing the remaining electron in the 4s subshell.
5. Express the final electron configuration in the format: \$1\text{s}^2 2\text{s}^2 2\text{p}^6 3\text{s}^2 3\text{p}^6 4\text{s}^1$, which represents the ground-state electron configuration of potassium.