What is the ground-state electron configuration of boron (B, atomic number 5)?

• A. $1^s{2}^s{2}^p$
• B. $1^s{2}^s{2}^p$
• C. $1^s{2}^s{2}^p$
• D. $1^s{2}^s{2}^p$

Answer: (C)

Verified step by step guidance

1. Identify the atomic number of boron, which is 5. This means boron has 5 electrons to place in its electron configuration.
2. Recall the order in which electron orbitals are filled according to the Aufbau principle: electrons fill orbitals starting from the lowest energy level to higher ones. The order begins with 1s, then 2s, then 2p.
3. Fill the 1s orbital first, which can hold up to 2 electrons. So, place 2 electrons in 1s: \$1\text{s}^2$.
4. Next, fill the 2s orbital, which can also hold up to 2 electrons. Place 2 electrons in 2s: \$2\text{s}^2$.
5. Finally, place the remaining 1 electron in the 2p orbital, since boron has 5 electrons total. This gives \$2\text{p}^1\(. Combine all to write the full ground-state electron configuration: \)1\text{s}^2 2\text{s}^2 2\text{p}^1$.