Yes, the number of neutrons in an atom can be determined by rounding the atomic mass and then subtracting the number of protons. The atomic mass of an element represents the combined mass of protons and neutrons in the nucleus of an atom. Since the atomic mass is typically provided as a decimal number on the periodic table, rounding it to the nearest whole number gives an approximation of the total number of protons and neutrons in the nucleus.
By subtracting the number of protons (which is equal to the atomic number of the element) from the rounded atomic mass, you can estimate the number of neutrons. However, it's important to note that this method provides an approximate value due to the presence of isotopes. Isotopes are atoms of the same element that have different numbers of neutrons. The atomic mass listed on the periodic table represents the weighted average of the masses of all the naturally occurring isotopes of that element.
If you need an accurate count of neutrons for a specific isotope of an element, you would need to refer to a more detailed source, such as a nuclear physics database or a specific isotope table, which provides the exact number of neutrons for each isotope.