Question

What is the atomic mass of Neon?

Answer 1

Hint :The naturally occurring isotopes of Neon are ${}^{20}Ne,{}^{21}Ne,{}^{22}Ne$ and have atomic masses $19.9924\text{ amu, 20}\text{.9940 amu, 21}\text{.9914 amu}$ respectively. Their natural abundance are $90.92\mathrm{\%},0.0257\mathrm{\%}\text{ and 8}\text{.82\% }$ .

Complete Step By Step Answer:
A single atom's atomic mass is simply its total mass, which is usually expressed in atomic mass units, or amu. A single carbon atom with six neutrons, carbon-12, has an atomic mass of 12 amu by definition. Other atoms' atomic masses aren't typically round numbers. However, in most cases, an atom's atomic mass would be very similar to its mass number, with some variation in decimal places.
Since an element may have several isotopes, each with their own atomic mass, we calculate the relative atomic mass—also known as the atomic weight—for that element. The relative atomic mass is the sum of all the different isotopes' atomic masses in a sample, with each isotope's contribution to the average measured by how much of the sample it makes up.
The relative atomic masses given in periodic table entries are calculated for all of each element's naturally occurring isotopes, weighted by their abundance on Earth. Asteroids and meteors, for example, can have very different isotope abundances.
Since, Neon has three naturally occurring isotopes ${}^{20}Ne,{}^{21}Ne,{}^{22}Ne$ , its atomic mass is calculated as the sum of atomic mass of an isotope multiplied by the percentage abundance of that isotope. So, relative atomic mass of Neon would be, $N{e}_{\text{Avg}\text{. atomic mass}}=19.9924\times {\displaystyle \frac{90.92}{100}}+20.9940\times {\displaystyle \frac{0.0257}{100}}+21.9914\times {\displaystyle \frac{8.82}{100}}$
 $\Rightarrow N{e}_{\text{Avg}\text{. atomic mass}}=20.18\text{ amu}$
Hence, the atomic mass of Neon is 20.18 amu.

Note :
Remember that the atomic mass of an element is less than the total mass of individual protons, neutrons and electrons. Because some amount of energy is needed to hold the subatomic particles together. The relation $E=m{c}^2$ tells us that mass is converted to energy and that energy is holding these particles together.