Answer:
D
Step-by-step explanation:
D) All of these answers explain the difference between mass number and average atomic mass.
Step-by-step explanation:
A) The mass number, which represents the total number of protons and neutrons in an atom's nucleus, is typically a whole number because protons and neutrons are discrete particles. When calculating the number of neutrons in an atom, chemists often need to round the atomic mass to the nearest whole number, as the mass number itself is a whole number. In contrast, the average atomic mass considers the contributions of various isotopes of an element, which can have different masses due to varying numbers of neutrons. The average atomic mass is not rounded in the same way.
B) The mass number is indeed a whole number, as it represents the sum of protons and neutrons, both of which have nearly integer masses. On the other hand, the average atomic mass considers the relative abundance of different isotopes of an element, and these isotopes can have slightly different masses due to the presence of different numbers of neutrons. This variation leads to the average atomic mass having a decimal value.
C) The mass number specifically refers to the sum of protons and neutrons in an atom's nucleus. It is a whole number because protons and neutrons each have nearly integer masses. In contrast, the average atomic mass takes into account the various isotopes of an element, each with its own distinct number of neutrons. This leads to differences in mass between isotopes and results in the average atomic mass being a weighted average of the masses of all the isotopes, which can have decimal values.
Therefore, all three explanations (A, B, and C) together cover the differences between mass number and average atomic mass.