High School

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------------------------------------------------ Gold has an atomic mass of 197 and an atomic number of 79. How many neutrons does it have?

A. 118
B. 276
C. 197
D. 79

Answer :

To find the number of neutrons in an atom, you need to know the atomic mass and the atomic number of the element.

1. Identify the Atomic Mass and Atomic Number:
- The atomic mass of gold is given as 197.
- The atomic number of gold is 79.

2. Understand What Each Term Means:
- Atomic number represents the number of protons in the nucleus of an atom.
- Atomic mass is approximately the total number of protons and neutrons in the atom.

3. Calculate the Number of Neutrons:
- To find the number of neutrons, you subtract the atomic number from the atomic mass:
[tex]\[
\text{Number of Neutrons} = \text{Atomic Mass} - \text{Atomic Number}
\][/tex]
- For gold, this calculation would be:
[tex]\[
197 - 79 = 118
\][/tex]

4. Conclusion:
- Gold has 118 neutrons in its nucleus.

So, the correct answer is that gold has 118 neutrons.