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Answer: Atomic mass is the total mass of a single atom of any specific element. A unified atomic mass unit is the unit of atomic mass, and this unit is denoted by the symbol “u”. The atomic mass is similar to the value of mass number because it is the protons and neutrons which collectively make up the atomic mass of a given element.
Carbon belongs to the 14th group of elements having an atomic number of 6 and a mass number of 12. Atomic mass is 12.01gmol-1 and denoted by the symbol ‘C’.
Carbon has three isotopes:
- C12 isotope (Stable)
- C13 isotope
- C14 isotope (Radioactive)
The numbers 12,13,14 represent the atomic mass of different carbon isotopes.
Now let’s look at the method to calculate the atomic mass of Carbon:
#If the given sample contains the isotopes of different percentages of the given element, this formula can be used.
The steps are:
1: First, you have to multiply the percentage of elements present by the given element’s atomic mass, and the result obtained should be divided by 100.
2: You have to add the values obtained from the first step for each given isotope.
Carbon atoms comprise 98.93% 12 C (12 u) and 1.07% 13 C(13.003 u).
We have to assume that there are 10 000 atoms of carbon, and accordingly, we’ll have 9893 atoms of 12 C and 107 atoms of 13C.
=>Mass of 12 C = 9893 atoms × 12 u /1 atom
=118716u
=>Mass of 13 C = 107 atoms × 13.003 /1 atom
=118716 u
Total mass= 120110 u
=>Average mass = 120 110 u / 10 000 atoms
= 12.011u
“The average atomic mass of carbon is 12.011 amu.”
