Which of the following statements about atoms is NOT correct? — Atomic Structure Chemistry Question

STEPS:

1. Analyze the Definition of an Element: The identity of a specific chemical element is determined solely by its atomic number, which is the number of protons in the nucleus.
2. Evaluate the Role of Neutrons: Atoms of the same element can have different numbers of neutrons; these variations are known as isotopes. For example, Carbon^-12 and Carbon^-14 both have 6 protons but different numbers of neutrons.
3. Evaluate the Role of Electrons: Atoms can gain or lose electrons to become ions without changing their identity as a specific element.
4. Identify the False Statement: Because an element can exist as different isotopes (varying neutrons) or ions (varying electrons), it is incorrect to state that all atoms of an element *must* have the same number of neutrons and electrons.
5. Conclusion: Therefore, statement B is the only incorrect statement among the choices.

WHY_OTHERS_WRONG:

• A: This is a correct statement; in a neutral atom, the positive charge of the protons is exactly balanced by the negative charge of an equal number of electrons.
• C: This is correct; according to modern atomic theory, the nucleus is incredibly small, and the vast majority of an atom's volume is the "empty space" occupied by the electron cloud.
• D: This is correct; the nucleus contains protons, which are positively charged, and neutrons, which are neutral, resulting in a net positive charge.
• E: This is correct; protons and neutrons each have a mass of approximately 1 amu, while electrons have a negligible mass (about 1/1800th of a proton), meaning the nucleus contains virtually all the mass.