An isotope has an atomic number of 15 and a mass number of 31. The number of protons it contains is
Answer Details
The atomic number of an element is the number of protons it has in its nucleus. The atomic number of the isotope is given as 15, which means it contains 15 protons. The mass number of the isotope is given as 31, which is the sum of the number of protons and neutrons in the nucleus.
Since the mass number is 31 and the atomic number is 15, the number of neutrons can be found by subtracting the atomic number from the mass number:
number of neutrons = mass number - atomic number
number of neutrons = 31 - 15
number of neutrons = 16
Therefore, the isotope has 15 protons, which is the same as its atomic number. Answer option (B) is correct.