Question

Define mass number & how they apply to isotopes

a) The number of protons in an atom; isotopes have the same mass number.

b) The total number of particles in an atom; isotopes have the same mass number.

c) The sum of protons and neutrons in an atom; isotopes have different mass numbers.

d) The number of neutrons in an atom; isotopes have different atomic and mass numbers.

Answer 1

The mass number is the sum of protons and neutrons in an atom; isotopes of an element have the same atomic number but different mass numbers due to variations in their neutron counts.

Step-by-step explanation:

The mass number is the sum of the number of protons and neutrons in an atom's nucleus. Answer choice c is correct: The mass number is the sum of protons and neutrons in an atom; isotopes have different mass numbers. Isotopes are atoms of the same element, meaning they have the same atomic number (same number of protons) but differ in the number of neutrons, resulting in a different mass number. For instance, carbon-12 and carbon-13 are isotopes of carbon, both with 6 protons, but carbon-12 has 6 neutrons and carbon-13 has 7 neutrons, giving them mass numbers of 12 and 13, respectively.

To find the number of neutrons in an atom, you subtract the atomic number from the mass number. Since the mass number of isotopes varies due to the difference in neutron count, isotopes of an element have the same atomic number but distinct mass numbers.