The number of neutrons in an element is obtained from the difference between the number of atomic masses and the number of atoms.
That is, neutron number (n) = atomic mass number (A) – atomic number (Z)
We know that the atomic number of potassium is 19 and the atomic average mass number is about 39. Neutron = 39 – 19 = 20. Therefore, a potassium atom has twenty neutrons.
|Mass number (A)||Atomic number (Z)||Neutron number = A – Z|
Based on the atomic number, mass number, and neutron number of the element, three things can be considered. These are isotope, isobar, and isotone. The number of neutrons depends on the isotope of the atom.
List of neutron numbers by an isotope of aluminum
Atoms that have the same number of protons but different mass numbers are called isotopes of each other. The English chemist Frederick Sodi first came up with the idea of isotopes in 1912, and the scientist Aston in 1919 identified two different mass neon atoms (20Ne, 22Ne).
He named the atoms with different masses of the same element as isotopes of that element. The number of protons in an isotope atom does not change but the number of neutrons does.
|Isotope||Mass number (A)||Atomic number (Z)||Neutron number = A – Z|
The potassium atom has about more than twenty-six isotopes. Among the isotopes, 39K and 41K are stable and formed naturally. The remaining isotopes of potassium are highly unstable and their half-lives are very short.
Of the 27 radioisotopes of potassium, the longest-lived radioisotope is 40K with a half-life of 1.248 × 109 years. All others are under a minute, most under a second. The mass of stable 39K is about 39 (38.9637064), and 41K is about 41.