The isotopic distribution of carbon on the Earth is roughly 99% carbon 12 (with 6 protons and 6 neutrons) and 1% carbon 13 (with 6 protons and 7 neutrons).
These isotopes are stable, which is why they are with us today, but unstable isotopes are also present in minute amounts.
Characteristics: Potassium is silvery-white, low melting, metal soft enough to be easily cut with a knife.
It tarnishes rapidly in air, forming a dull oxide coating. It is extremely reactive, reacting violently with water, for example, to produce hydrogen gas and potassium hydroxide.
In people whose urinary excretion of potassium is impaired, a potassium intake below 4.7 g (120 mmol)/day is appropriate because of adverse cardiac effects.If the digestive system is bypassed and potassium salts are injected into a vein, the heart can be stopped.Due to its highly reactive nature, elemental potassium must be handled with extreme care.A timber found in a home built 5730 years ago (one half life) would have half the C in the Earth's atmosphere has remained constant.As a first approximation one can assume this, but more accurate results must take into account fluctuations in the intensity of the cosmic rays entering the Earth's atmosphere.