Why is the atomic mass of iron, 55.845 amu, most similar to the mass of iron-56, yet less than 56 amu? The atomic mass is the simple average of the masses of the two most abundant isotopes. Iron‑56 is the most abundant isotope, so the atomic mass of iron is most similar to the mass of iron‑56. The second most abundant isotope is iron‑54, which reduces the atomic mass to less than 56 amu. The atomic mass is the weighted average of the masses of all of the isotopes. Iron‑56 is the most abundant isotope, so the atomic mass of iron is most similar to the mass of iron‑56. The second most abundant isotope is iron‑54, which reduces the atomic mass to less than 56 amu. The atomic mass is the weighted average of the masses of the two most abundant isotopes. Iron‑56 is the most abundant isotope, so the atomic mass of iron is most similar to the mass of iron‑56. The second most abundant isotope is iron‑54, which reduces the atomic mass to less than 56 amu. The atomic mass is the simple average of the masses of all of the isotopes. Iron‑56 is the most abundant isotope, so the atomic mass of iron is most similar to the mass of iron‑56. The second most abundant isotope is iron‑54, which reduces the atomic mass to less than 56 amu.

Iron‑56 is the most abundant isotope, so the atomic mass of iron is most similar to the mass of iron‑56.

Explanation:

The atomic abundance of the isotopes of Iron is:

⁵⁴Fe: 5.82%

⁵⁶Fe: 91.66%

⁵⁷Fe: 2.19%

⁵⁸Fe: 0.33%

Where the Iron-56 is the most abundant isotope of Iron atom

As atomic mass is defined as the sum of the masses of the ions multiplied by its abundance, and the Iron-56 is the most abundance isotope, the atomic mass of Fe most be similar to the ⁵⁶Fe mass because is the most abundant isotope.

Right option is:

the electronic configuration of an atom with eight electrons is 1s²2s²2p⁴. the orbital diagrams are shown in the figure.

as per the hunds rule:

1. electrons tend to avoid being in the same orbital as per as practicable.

2. electrons in different orbitals of the same energy will have their spin parallel.

this can be illustrated from the multiplicity of the orbitals of the atom. as there are four electrons in the p orbital and p orbital has 3 sub-shells. the electrons can be fed in different ways as shown in the figure but the correct orbital diagram will be as per the hunds rule.

the number of valence electrons for each molecule or ion is shown beneath the structure. remember hydrogen will not have more than two electrons. this hydrogen is part of a covalent bond (sharing two electrons). a double bond here would cause hydrogen to share four electrons with phosphorus.