Answer:
1: 38
2: 39
3: 40
4: 41
Step-by-step explanation:
The mass in amu is the weight of the neutrons and protons in the element. The mass number is the number neutrons and protons you have in an element. Both neutrons and protons have a weight of 1 amu. Since you can't have a decimal of a subatomic particle, you have to round to the nearest whole number.