The notion that elementary particles have charges that come in fractions like -1/3, +2/3, and -1 is a consequence of the theory known as the Standard Model of particle physics. The Standard Model describes the fundamental particles and their interactions.
In the Standard Model, particles are categorized into two broad classes: fermions and bosons. Fermions are the building blocks of matter, and they are divided into two groups: quarks and leptons. Quarks are the constituents of protons and neutrons, while electrons are an example of leptons.
Quarks come in six different types, or flavors: up, down, charm, strange, top, and bottom. Each flavor of quark carries a fractional electric charge. The up quark has a charge of +2/3, while the down quark has a charge of -1/3. The charges of other quarks are also fractional, but they differ in the overall magnitudes.
On the other hand, leptons, such as the electron, carry charges of either +1 or -1. The electron has a charge of -1, while its electrically neutral partner, the neutrino, has a charge of 0.
The reason for the fractional charges of quarks and the whole number charges of leptons is still an open question in particle physics. However, it is important to note that quarks have never been observed in isolation due to a phenomenon called color confinement. Quarks are always found in combinations of three, forming baryons (such as protons and neutrons) or in pairs with their corresponding antiquarks, forming mesons.
The precise reasons for the specific values of the fractional charges and the difference between the charges of quarks and leptons are still subjects of ongoing research and theoretical investigation. These characteristics are deeply connected to the symmetries and properties of the fundamental forces described by the Standard Model. Explaining the origins of charge quantization and the specific values is an active area of study in particle physics, and it remains an exciting topic for future discoveries and theories.