In the heart of an atom, there lies the tiniest and yet most powerful blob in the universe. This blob is called the nucleus. The discovery of the nucleus was quite unexpected. Ernest Rutherford, in an attempt to know more about atoms, put together the alpha-gold foil experiment. In this experiment, a thin gold foil (that would be a few atoms thick) will be bombarded with positively charged beams (alpha-rays). Most of the beams passed through the gold foil, making Rutherford believe that the atom is mostly empty space. The most exciting part of the experiment, however, was the few beams that got deflected and bounced back. These beams hit something solid and positively charged. It was the nucleus.

The nucleus is not just the central part of the atom. The nucleus can be viewed as the heart of the atom. It contains two of the three subatomic particles: protons and neutrons. The protons are positively charged and the number of protons identify the atom. For example, if there are six protons in the nucleus, the atom cannot be anything else but carbon. The neutrons, on the other hand, have no charge but it does have a mass that is almost equal to that of the proton. Together, the protons and neutrons make up the mass of an atom. The mass of the third subatomic particle, the electron, is insignificant and many atoms can easily remove electrons during chemical reactions.

Then, as quantum physics developed, scientists discovered that the heart of the atom has more than protons and neutrons. Protons and neutrons are just types of hadrons, which are the heavy elementary particles that are made of three quarks. Strong attractive forces, perhaps the strongest in the universe, hold together the hadrons and other elementary particles (mesons and baryons) within the atom’s nucleus.

We’d like to thank Miss Sue Lang on this contribution to our web page.