Atom

An atom is a unit of matter composed of a nucleus and electron orbitals. The nucleus is the core of the atom, which contains the majority of the atom's mass. It's held together by the strong force and electromagnetism, and is finally composed of particles called protons and neutrons, which are present in equal amounts (the more of each, the heavier the atom, and thus the weight of the element). The second half of an atom is the orbitals, which consume the most volume in the atom, and are responsible for both the formation of bonds, and the contact forces (such as friction, which prevents you from falling through the ground). The orbitals are held to the nucleus by electromagnetism, and they are essentially an area which contains the electrons. Protons and neutrons are composite particles, and they are made of quarks held together by gluons. Protons and neutrons are the building blocks of the nucleus. Protons and neutrons (as well as other composite particles) are made of fundamental particles, which are the smallest forms of matter, held together by gluons. These particular particles are quarks, coming in several "flavours" and colours (or rotations and charge). Gluons bond them together by changing the colours of the quarks, which cause them to be affected by the strong force (or them being attracted to each other). In summary, atoms are made of nuclei (and electrons), nuclei are made of hadrons or composites, and finally, hadrons are made of gluons and quarks.