Carbon-12

Carbon-12, written as ¹²C, is the most common form of carbon on Earth. It makes up almost all carbon because it is made in stars through a process called the triple-alpha process. Carbon-12 is very important because scientists use it as a standard to measure the weights of all atoms. Its weight is exactly 12 daltons.

Carbon-12 has 6 protons, 6 neutrons, and 6 electrons. It is one of two stable types of carbon, with carbon-13 being the other.

History

Before 1959, scientists used oxygen to explain the idea of a mole. In 1959–60, two important groups agreed to change this. They decided a mole would be based on carbon-12 instead. This new way was officially accepted in 1967 and 1971.

In 1961, carbon-12 became the new standard for measuring the weight of all other elements. Later, in 1980, they made sure the carbon-12 atoms were not connected to anything else. In 2018, scientists gave an exact number for how many tiny particles are in a mole.

Hoyle state

The Hoyle state is an excited form of carbon-12. It was predicted in 1954 and helps create carbon in stars. This state forms when a helium nucleus fuses with another nucleus in very hot and dense conditions. The Hoyle state is very short-lived and usually breaks apart back into three helium particles, but sometimes it releases energy as light.