karbon12atom

Carbon-12, denoted 12C, is a stable isotope of the element carbon. It has six protons and six neutrons in its nucleus, giving it a mass number of 12. In a neutral atom, there are six electrons arranged in the usual atomic orbitals (electronic configuration 1s2 2s2 2p2). The combination of protons, neutrons, and electrons yields a mass near 12 atomic mass units (u) for the neutral atom.

The 12C isotope plays a central role in the definition of atomic mass and the mass scale used in chemistry. The atomic mass unit is defined as exactly 1/12 of the mass of a neutral 12C atom in its ground state, which makes 12C the reference standard for atomic masses. Consequently, the concept of the mole is tied to this standard through Avogadro’s constant; one mole of 12C atoms has a mass of exactly 12 grams. This baseline underpins precise mass measurements and isotope comparisons in analytical techniques such as mass spectrometry.

Natural abundance of carbon shows 12C as the predominant isotope, making up about 98.93% of terrestrial carbon. About 1.07% is 13C, with trace amounts of radioactive 14C present due to cosmic ray interactions. 12C is foundational to organic chemistry and biology, as carbon-12 atoms are the most common building blocks in organic molecules on Earth and serve as a reference standard in many isotopic and mass-related analyses.