Question

look at the model. then, choose the best answers.
5 choose the best answer.
how many energy levels does boron have?
1
2
4
3
6 choose the best answer.
how many valence electrons does boron have?
9
2
5
3

Explanation:

• For the first question: The number of energy levels (shells) an atom has is determined by its period in the periodic table. Boron is in period 2, so it has 2 energy levels.
• For the second question: Valence electrons are the electrons in the outermost shell. Boron has an electron configuration of \(1s^{2}2s^{2}2p^{1}\). The outermost (second) shell has \(2 + 1=3\) electrons.

Answer:

1. 2
2. 3