Final answer:
Nitrogen, with an atomic number of 7, likely has two electron shells.
Step-by-step explanation:
Nitrogen has an atomic number of 7, which represents the number of protons in its nucleus. The atomic number also indicates the number of electrons in a neutral atom. In a neutral atom, the number of electrons is equal to the number of protons.
Since nitrogen has 7 electrons, it is likely to have 2 electron shells. The first shell can accommodate a maximum of 2 electrons, while the second shell can accommodate a maximum of 8 electrons. In the case of nitrogen, the first shell is filled with 2 electrons and the second shell is filled with 5 electrons, totaling 7 electrons.
Therefore, the correct answer is b. two electron shells.