<< Chapter < Page Chapter >> Page >

Art connection

Carbon is indicated by its atomic symbol, a capital C. Carbon has the atomic number six and two stable isotopes, carbon-12 and carbon-13.
Carbon has an atomic number of six, and two stable isotopes with mass numbers of twelve and thirteen, respectively. Its relative atomic mass is 12.011

How many neutrons do carbon-12 and carbon-13 have, respectively?


Isotopes are different forms of an element that have the same number of protons but a different number of neutrons. Some elements—such as carbon, potassium, and uranium—have naturally occurring isotopes. Carbon-12 contains six protons, six neutrons, and six electrons; therefore, it has a mass number of 12 (six protons and six neutrons). Carbon-14 contains six protons, eight neutrons, and six electrons; its atomic mass is 14 (six protons and eight neutrons). These two alternate forms of carbon are isotopes. Some isotopes may emit neutrons, protons, and electrons, and attain a more stable atomic configuration (lower level of potential energy); these are radioactive isotopes, or radioisotopes . Radioactive decay (carbon-14 losing neutrons to eventually become carbon-12) describes the energy loss that occurs when an unstable atom’s nucleus releases radiation.

Evolution connection

Carbon dating

Carbon is normally present in the atmosphere in the form of gaseous compounds like carbon dioxide and methane. Carbon-14 ( 14 C) is a naturally occurring radioisotope that is created in the atmosphere from atmospheric 14 N (nitrogen) by the addition of a neutron and the loss of a proton because of cosmic rays. This is a continuous process, so more 14 C is always being created. As a living organism incorporates 14 C initially as carbon dioxide fixed in the process of photosynthesis, the relative amount of 14 C in its body is equal to the concentration of 14 C in the atmosphere. When an organism dies, it is no longer ingesting 14 C, so the ratio between 14 C and 12 C will decline as 14 C decays gradually to 14 N by a process called beta decay—the emission of electrons or positrons. This decay gives off energy in a slow process.

After approximately 5,730 years, half of the starting concentration of 14 C will have been converted back to 14 N. The time it takes for half of the original concentration of an isotope to decay back to its more stable form is called its half-life. Because the half-life of 14 C is long, it is used to date formerly living objects such as old bones or wood. Comparing the ratio of the 14 C concentration found in an object to the amount of 14 C detected in the atmosphere, the amount of the isotope that has not yet decayed can be determined. On the basis of this amount, the age of the material, such as the pygmy mammoth shown in [link] , can be calculated with accuracy if it is not much older than about 50,000 years. Other elements have isotopes with different half lives. For example, 40 K (potassium-40) has a half-life of 1.25 billion years, and 235 U (Uranium 235) has a half-life of about 700 million years. Through the use of radiometric dating, scientists can study the age of fossils or other remains of extinct organisms to understand how organisms have evolved from earlier species.

Photo shows scientists unearthing a mammoth skeleton.
The age of carbon-containing remains less than about 50,000 years old, such as this pygmy mammoth, can be determined using carbon dating. (credit: Bill Faulkner, NPS)

Questions & Answers

Describe the process of protein sythesis?
Kizito Reply
What is a ploidy level
Francis Reply
Ploidy refers to the number of chromosomes. We have 23 pairs of chromosomes in somatic cells. Sex cells are haploid thus 23 chromosomes vs. 46 Chromosomes.
Evolution is evolvement according to one's environment. Let's use humidity as an example. A person from a very cold environment would not be used to hot humid weather. But over time their body would slowly, slowly adapt.
Give me (3) types of biodiversity
Hi guys 🇧🇪
hello boy
what do you guys understand about evolution?
Kiana Reply
it's a process or analayzing some program
but am not sure if some know plz let share
is a study of
unfolding or unrolling hence the process of development of growth
is the periodic change of the structural features of an organism
I think
process of developing
hi guiz
hello guys
why are diagrams not available
Evans Reply
How can nucleotide molecules of DNA be constructed?construct a six molecules of DNA?
Julia Reply
You take a Deoxyribose sugar. The Deoxyribose sugar has a hydrogen on the second carbon vs. an OH group. The nitrogenous base binds to the #1 Carbon and a phosphate binds to the 5'. When the 2nd NBase bonds, it does so on the 3' Carbon. Thus you have 5' to 3' directional growth.
what is the explanation of local biomes in Nigeria
It would be savanna, tropical grassland.
describe the breathing mechanism in the body fish.
Jackson Reply
what is genetics.
the study of hereditary
state the importance of biodiversity of organisms in an area?
Chris Reply
Let's compare The Brazilian Rain Forest to Antarctica. There many, many types of flora and fona in The Rain Forest. So many that we are still discovering them vs. the variety in Antarctica.
it boosts the ecosystem where each species has an important tole
what is biology
Adam Reply
Biology is the study of living things.
what are some of the branches of biology?
what is meosis
Mabatho Reply
did you mean meiosis? meiosis this is the type of cell division where one diploid parent cell produces two daughter cells that are haploid and genetically different from the parent cell.
I'm struggling to understand genetics
Am also struggling as well
nothing comes on a silver platter, you need to put effort in everything you are doing not forgetting God. study as if there is no tomorrow. "Suffer now and enjoy the future"
true bro
exactly brother
Glory to God
Thanks Pat🙏
you're welcome
what's a nervous system
tessy Reply
what's the human brain
The human brain consist of the cerebrum, cerebellum and brain stem. The cerebral cortex is composed of neuronal cell bodies, which is the gray matter. The white matter is composed of neuronal axons. The brain is the motherboard of our system.
the structure of paramecium
Charity Reply
It is a unicellular, eukaryotic, autotrophic, organism whose movement is done by cilia.
what is codominant
what is endocytosis
Stephen Reply
Endocytosis is when the cell membrane surrounds and engulfs an antigen, viral particles, etc. This forms a vesicle which moves through the cytoplasm. And merges with a designated organelle.
what is the meaning of adrenocorticotropic
Abigail Reply
adrenocorticotropic is stimulating or acting on the adrenal cortex.
ok thanks
What is science of biology
Thando Reply
The study 📓 of leaving things
how does a parasite benefit from its mode of living?
Abuk Reply
why are the images n diagrams unable to be seen?
where are the illustrations
a parasite gets protection, food, shelter
human being

Get the best Biology course in your pocket!

Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Biology' conversation and receive update notifications?