It has an atomic number of 6 and an atomic mass of 12 uma. Allmost all carbon atoms are an isotope containing 6 neutrons, 12C. It is a group 14 non-metal, which means that each atom establishises a discernable amount of covalent bonds with, instead of creating a "sea of electrons" like transition metals do.
With an electronic configuration of [He]2s2p2, carbon has four valence electrons, which means that it can share pairs of electrons with up to 4 distinct atoms, forming covalent bonds with each. In order to that however, the orbitals of the valence electrons must undergo sp3 hibridization first.
Unlike other members of its group such as silicon, germanium, tin, lead and flerovium, the small radius of each atom allows lateral overlapping of non-hybridized orbitals, thus carbon can easily form double and triple bonds with itself and other elements.
Since each atom is quite small, inter-atomic attraction is stronger and carbon bonds have dissociation energies. A mol of C-C bonds need 346 kJ to break. Pi-type bonds can allow double and triple bonds, with dissociation energies of 602 and 835 kJ respectively within carbon atoms. Besides, bonds with hydrogen, nitrogen, oxygen, sulfur, phosphorous and halogenic elements have energy values similar to a C-C bond.
Pure carbon comes in a variety of forms, distinguishable by the internal arrangement of its atoms, called allotropes. At standard conditions (pressure of 101,325 Pa and temperature of 298.15 K), graphite is the most thermodynamically stable allotrope, having its atoms positioned in hexagonal grids arranged in lattices. Any other allotrope, such as diamond, is thermodynamically unstable and eventually becomes graphite.