Gold has an atomic number of 79 and a mass number of 197. How many neutrons does a typical atom of gold contain?

• A. 276
• B. 118
• C. 197
• D. 79

Answer: (B)

Verified step by step guidance

1. Identify the atomic number (Z) of gold, which is given as 79. The atomic number represents the number of protons in the nucleus of the atom.
2. Identify the mass number (A) of gold, which is given as 197. The mass number represents the total number of protons and neutrons in the nucleus.
3. Recall the relationship between mass number, atomic number, and number of neutrons: \(\text{Number of neutrons} = A - Z\).
4. Substitute the given values into the formula: \(\text{Number of neutrons} = 197 - 79\).
5. Calculate the difference to find the number of neutrons in a typical gold atom.