Question

if an atom of gold (au) contains 79 protons and 118 neutrons, what is its atomic mass?
○ 79
○ 39
○ 118
○ 197

Explanation:

Step1: Recall atomic mass formula

Atomic mass is approximately the sum of protons and neutrons. So, formula: \( \text{Atomic Mass} = \text{Number of Protons} + \text{Number of Neutrons} \)

Step2: Substitute values

Protons = 79, Neutrons = 118. So, \( 79 + 118 = 197 \)

Answer:

197 (corresponding to the option with 197)