A Level Physics Practice Exam

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Study for the A Level Physics Exam. Our quiz features flashcards and multiple choice questions, each with hints and explanations. Prepare thoroughly!

Each practice test/flash card set has 50 randomly selected questions from a bank of over 500. You'll get a new set of questions each time!

Practice this question and more.

In atomic structure, what does the term 'mass number' refer to?

The total number of protons
The total number of electrons
The total number of protons and neutrons
The total number of neutrons

The correct answer is: The total number of protons and neutrons

The term 'mass number' refers specifically to the total number of protons and neutrons in an atomic nucleus. This value is significant because it represents the overall mass of the atom, as protons and neutrons contribute nearly all of the atomic mass, while the mass of electrons is negligible in comparison. Understanding the mass number is key for identifying isotopes of elements, as isotopes of an element will have the same number of protons (thus the same atomic number) but different mass numbers due to varying numbers of neutrons. This aspect is crucial in fields such as chemistry and nuclear physics, where the behavior of isotopes can significantly influence reactions and stability.