Potassium-40 is a radioactive isotope of potassium that is present in the human body. How many neutrons are present in its nucleus?
The correct answer and explanation is:
Correct Answer:
Potassium-40 has 21 neutrons in its nucleus.
Explanation:
To determine the number of neutrons in an atom, subtract the atomic number from the mass number. The atomic number is the number of protons and is unique to each element. For potassium, the atomic number is 19. This means potassium has 19 protons in its nucleus.
Potassium-40 is a specific isotope of potassium, and its mass number is 40. The mass number is the sum of protons and neutrons in the nucleus. Therefore, to find the number of neutrons in potassium-40, use the following formula:
Number of neutrons = Mass number − Atomic number
= 40 − 19
= 21
So, potassium-40 has 21 neutrons.
Potassium-40 is a naturally occurring radioactive isotope. Though it only makes up a tiny fraction (about 0.012%) of natural potassium, it plays an important role in natural radioactivity in the environment and even within the human body. Since potassium is a necessary nutrient and is found in all living cells, small amounts of potassium-40 are also present in living organisms, including humans.
Potassium-40 decays over time through two main pathways: it can decay to calcium-40 by beta decay or to argon-40 by electron capture. This decay process releases radiation, which contributes to the background radiation dose people are naturally exposed to. Despite being radioactive, the amount of potassium-40 in the body is so low that it poses no health risk under normal conditions.
Understanding the structure and properties of isotopes like potassium-40 is important in fields such as nuclear physics, medicine, and geology. In fact, potassium-40 is used in radiometric dating to determine the age of rocks and minerals, particularly in geochronology.