Explanation:
Atomic number is defined as the number of protons present in a neutral atom. Whereas mass number is defined as the sum of total number of protons and neutrons present in an atom.
For example, in the given periodic table entry for iron the atomic number of iron is 26.
Also, it is known that in a neutral atom the number of protons equal the number of electrons.
Therefore, there are 26 electrons in the given neutral iron atom.
Hence, we can conclude that the atomic number for iron is 26. The number of electrons in a neutral iron atom is 26.