If atom X has an atomic number of 74, which of the following statements is correct?

• A. Atom X is the element gold (Au).
• B. Atom X has a mass number of 74.
• C. Atom X has 74 neutrons in its nucleus.
• D. Atom X has 74 protons in its nucleus.

Answer: (D)

Verified step by step guidance

1. Recall that the atomic number of an element is defined as the number of protons in the nucleus of its atoms.
2. Identify that atom X has an atomic number of 74, which means it has 74 protons in its nucleus.
3. Understand that the atomic number uniquely identifies the element, so atom X corresponds to the element with atomic number 74, which is tungsten (W), not gold (Au).
4. Recognize that the mass number is the sum of protons and neutrons, so having an atomic number of 74 does not imply the mass number is 74.
5. Note that the number of neutrons is not necessarily equal to the atomic number; it depends on the isotope, so atom X does not necessarily have 74 neutrons.