The element iron (Fe) has an atomic number of 26, which means it has 26 protons in its nucleus. In its most common isotope, iron-56 (Fe-56), there are also 30 neutrons. The number of neutrons can vary in different isotopes of iron, but the atomic number always remains the same, defining the element.
Regarding the second part of your question, the strong nuclear force is responsible for holding the protons together in the nucleus. This force is one of the fundamental forces of nature and is incredibly powerful but acts only over very short distances. The strong force overcomes the electrostatic repulsion between positively charged protons, which would otherwise cause the nucleus to collapse.
The strong force is highly attractive at close range, and as long as the protons and neutrons are within the range of this force, the nucleus remains stable. However, as the distance between nucleons (protons and neutrons) increases, the strong force weakens rapidly, and the electrostatic repulsion between protons becomes dominant.
To maintain stability, a balance must exist between the attractive strong force and the repulsive electrostatic force. This balance is achieved through the combination of protons and neutrons in the nucleus. Neutrons act as buffers, reducing the electrostatic repulsion between protons by adding an additional nuclear force while not adding any additional positive charge.
In summary, the strong force, along with the presence of neutrons, counteracts the electrostatic repulsion between protons, preventing the collapse of the nucleus and providing stability to the atom.