Phosphorus-31 is the most common isotope. (Wikipedia)
Carbon has a few isotopes. The most common naturally occurring isotope of it is C12. Mass number of it is 12.
The mass number of the most common hydrogen isotope, Hydrogen-1, is one
Carbon is a non metal element. Mass number of it is 12.
The mass number of zirconium-98 is 98 by definition: The number after a hyphen in the name of an isotope is the mass number of the isotope.
ChlorineMolar Mass: 35.5Most Abundant Isotope Mass: 35
The mass number of the most common titanium isotope is 48.
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Carbon has a few isotopes. The most common naturally occurring isotope of it is C12. Mass number of it is 12.
The most stable isotope of radium - 226Ra - has the atomic mass 226,025 409 8 (25).
39
The mass number of the most common hydrogen isotope, Hydrogen-1, is one
Mercury is a metal element. Mass number of it is 201.
Carbon is a non metal element. Mass number of it is 12.
Number of neutrons = Mass number of an isotope - 93The most common isotope has 144 neutrons.
Argon is a non metal element. Mass number of it is 40.
12
An isotope is member of an element of Mass Number differing from the average; for example, the most common isotope of Carbon is 12C (6 protons, 6 neutrons), where 13C and 14C would be less common (even unstable, radioactive) isotopes. So isotopes are varying forms of an element, differing in mass number.