Why is it impossible for an element to have an atomic number of 110.5?

Question

a. atoms of an element have the same whole number of protons and neutrons

b. atoms of an element all have the same whole number of protons

c. exactly half of the isotopes would need an atomic number of 110 and half would need an atomic number of 111 which is very unlikely

d. atoms with atomic numbers greater than 100 are unstable

Answer 1

The correct answer is:

b. atoms of an element all have the same whole number of protons

The atomic number of an element is defined as the number of protons in the nucleus of an atom of that element. Since the number of protons must be a whole number, an atomic number of 110.5 is impossible. All elements have a whole number of protons, which is why atomic numbers are always whole numbers.