Which discovery by Henry Moseley significantly advanced the understanding of atomic structure?

• A. He discovered the neutron as a subatomic particle.
• B. He determined that the atomic number is equal to the number of protons in the nucleus.
• C. He developed the plum pudding model of the atom.
• D. He proposed that electrons orbit the nucleus in fixed energy levels.

Answer: (B)

Verified step by step guidance

1. Understand the historical context of atomic structure discoveries before Moseley, such as the plum pudding model and the Bohr model, which involved electrons orbiting the nucleus.
2. Recognize that Henry Moseley's key contribution was related to the concept of atomic number, which was previously not clearly defined in terms of physical meaning.
3. Learn that Moseley used X-ray spectra to study elements and found a systematic relationship between the frequency of X-rays emitted and the atomic number, rather than atomic mass.
4. From Moseley's work, conclude that the atomic number corresponds to the number of protons in the nucleus, providing a clear and measurable property that defines each element.
5. Understand that this discovery helped organize the periodic table by atomic number and advanced the understanding of atomic structure by linking atomic number directly to nuclear charge.