Did Dmitri Mendeleev know about the existence of the atomic nucleus when he developed the periodic table?

• A. No, the nucleus was discovered after Mendeleev's work.
• B. Mendeleev was aware of protons and neutrons but not the nucleus.
• C. Mendeleev discovered the nucleus himself.
• D. Yes, Mendeleev incorporated the nucleus into his periodic table.

Answer: (A)

Verified step by step guidance

1. Understand the historical context: Dmitri Mendeleev developed the periodic table in 1869, before the discovery of the atomic nucleus.
2. Recall that the atomic nucleus was discovered by Ernest Rutherford in 1911, well after Mendeleev's time.
3. Recognize that Mendeleev arranged elements based on atomic mass and chemical properties, without knowledge of subatomic particles like protons, neutrons, or the nucleus.
4. Note that protons and neutrons were identified even later, with the neutron discovered in 1932, so Mendeleev could not have known about them.
5. Conclude that Mendeleev did not know about the atomic nucleus when he developed the periodic table.