Predict whether the total mass of the 26 protons and neutrons that make up the iron nucleus will be more, less, or equal to 55.845 amu, the mass of an iron atom from the periodic table. If it is not equal, explain why not.

The atomic mass unit (amu) is a standard unit of mass used to express atomic and molecular weights. One amu is defined as exactly one-twelfth of the mass of a carbon-12 atom. Since the carbon-12 atom has six protons and six neutrons, the mass of a single proton or neutron is roughly 1 amu.

In nuclear physics, the atomic mass unit provides a convenient means for expressing the mass of particles in atoms. When calculating the mass of an atom, we add up the masses of each proton, neutron, and electron to get the atomic weight. Electrons, however, have such a small mass (approximately 1/1836 amu) that their contribution to the total atomic weight is negligible. Therefore, for simplicity, atomic weights are often discussed in terms of just protons and neutrons.

Understanding the concept of amu is crucial when discussing nuclear masses and phenomena such as the mass defect, which is observed when comparing actual atomic masses to the sum of individual particle masses.

Protons and neutrons, collectively known as nucleons, are subatomic particles found in the nucleus of an atom. The number of protons within the nucleus defines the element and is referred to as the atomic number. Neutrons contribute to the mass of an atom but do not affect its chemical properties.

In an iron atom, for instance, there are 26 protons, which is characteristic of all iron atoms. The number of neutrons can vary, leading to different isotopes of iron. Isotopes have the same number of protons but different numbers of neutrons. A common isotope of iron, for example, has 30 neutrons.

The mass of protons and neutrons is almost identical and close to 1 amu. However, the combined mass of the protons and neutrons in an iron nucleus does not equal the mass listed for an iron atom, which includes corrections for mass defect and the tiny mass contributed by electrons.

Einstein's theory of relativity plays a vital role in explaining the mass defect observed in atomic nuclei. The most famous equation derived from this theory is \(E = mc^2\). It implies that energy (\