How many valence electrons does a boron (B) atom have?

• A. 3
• B. 5
• C. 4
• D. 2

Answer: (A)

Verified step by step guidance

1. Identify the atomic number of boron (B), which is 5. This means boron has 5 electrons in total.
2. Recall that valence electrons are the electrons in the outermost shell (energy level) of an atom.
3. Determine the electron configuration of boron: 1s\^2 2s\^2 2p\^1.
4. Recognize that the first shell (1s) is full and the valence electrons are in the second shell (2s and 2p orbitals).
5. Count the electrons in the outermost shell: 2 electrons in 2s and 1 electron in 2p, totaling 3 valence electrons.