Atoms are made up of up and down quarks and electrons because these particles are the basic building blocks that interact via fundamental forces to form stable, neutral atoms.
Quarks are elementary particles that possess fractional electric charges. Up quarks have a charge of +2/3 elementary charge (e), while down quarks have a charge of -1/3 e. Protons, which are found in the atomic nucleus, are composed of two up quarks and one down quark, resulting in a total charge of +1e. Neutrons, also found in the nucleus, consist of one up quark and two down quarks, resulting in a neutral charge (0e). The combination of up and down quarks within protons and neutrons gives rise to the stability of atomic nuclei.
Electrons, on the other hand, are negatively charged elementary particles that orbit the atomic nucleus. They are fundamental constituents of matter and have a charge of -1e. Electrons occupy specific energy levels or orbitals around the nucleus, forming a cloud-like electron cloud. The electrostatic attraction between the positively charged protons in the nucleus and the negatively charged electrons holds the atom together.
The interaction between electrons and the protons in the nucleus is primarily governed by the electromagnetic force, while the interactions between quarks within the nucleus are mediated by the strong nuclear force. These fundamental forces play a crucial role in keeping the atom stable by balancing the electric forces and ensuring that the atom does not collapse under its own electrostatic attraction.
The combination of up and down quarks in protons and neutrons, along with the presence of electrons, allows for the formation of neutral atoms. Different arrangements and combinations of protons, neutrons, and electrons give rise to different elements on the periodic table, each with its unique atomic number and properties.
In summary, the presence of up and down quarks within protons and neutrons, combined with the negatively charged electrons, enables the formation of electrically neutral atoms, which are the building blocks of matter as we commonly observe it.