If you know the number of protons in a neutral atom, which of the following pieces of information can NOT be determined?

• A. The number of electrons in the atom
• B. The number of neutrons in the atom
• C. The atomic number of the element
• D. The identity of the element

Answer: (B)

Verified step by step guidance

1. Understand that the number of protons in a neutral atom is equal to the atomic number (Z) of the element, which uniquely identifies the element.
2. Recognize that in a neutral atom, the number of electrons equals the number of protons, so knowing the number of protons allows you to determine the number of electrons.
3. Recall that the atomic number (Z) corresponds directly to the number of protons, so knowing the number of protons gives you the atomic number and thus the identity of the element.
4. Note that the number of neutrons is not fixed for a given element because atoms can have different numbers of neutrons, resulting in different isotopes.
5. Therefore, knowing only the number of protons does NOT allow you to determine the number of neutrons in the atom.