Answer:
Atomic mass of nitrogen = 14.0067 amu.
Explanation:
Isotopes can be defined as two or more forms of a chemical element that are made up of equal numbers of protons and electrons but different numbers of neutrons.
Generally, the isotopes of a chemical element have the same chemical properties because of their atomic number but different physical properties due to their atomic weight (mass number).
The two isotopes of nitrogen are nitrogen-14 and nitrogen-15.
Given the following data;
Relative abundance of N-14 = 99.63%
Atomic mass of N-14 = 14.003
Relative abundance of N-15 = 0.37%
Atomic mass of N-15 = 15.000
The atomic mass is;
14.003 × (99.63/100) + 15.000 × (0.37/100)
Atomic mass = 14.003 × (0.9963) + 15.000 × (0.0037)
Atomic mass = 13.9512 + 0.0555
Atomic mass = 14.0067 amu.
Therefore, the atomic mass of nitrogen is 14.0067 amu.
Considering the definition of atomic mass, isotopes and atomic mass of an element, the average mass of nitrogen is 14.0067 amu.
First of all, the mass number A of an atom is the sum of the number of protons and the number of neutrons in the atomic nucleus.
Being the number of protons the atomic number, the same chemical element can be made up of different atoms, that is, their atomic numbers are the same, but the number of neutrons is different. These atoms are called isotopes of the element.
On the other hand, the atomic mass of an element is the weighted average mass of its natural isotopes.
In other words, the atomic masses of chemical elements are usually calculated as the weighted average of the masses of the different isotopes of each element, taking into account the relative abundance of each of them.
In this case, you know that the two common isotopes of nitrogen have masses of 14.003 amu (99.63% abundance) and 15.000 amu (0.37%). Then, the average mass of lithium can be calculated as:
14.003 amu×0.9963 + 15.000 amu×0.0037= 14.0067 amu
Finally, the average mass of nitrogen is 14.0067 amu.
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