Question

The value of 1 amu is equal to:
A. $1.66\times {{10}^{-8}}g$
B. $1.66\times {{10}^{-4}}g$
C. $1.66\times {{10}^{-16}}g$
D. $1.66\times {{10}^{-24}}g$

Answer 1

Hint: Full form of amu is atomic mass unit. One atomic mass unit is defined as $\dfrac{1}{12}$times the mass of a carbon-12 atom. It is a unit of mass that is used when nuclear particles are concerned.

Complete step by step solution:
We know that atomic number is the number of protons in the atom’s nucleus, while atomic mass is the mass of the atom, which is the sum of the number of protons and neutrons. The atomic mass of an atom is expressed in atomic mass units. Atomic mass unit is defined as a unit of measurement for atoms and molecules like we use kilograms and grams for weighing in a grocery shop. Why are not using grams or kilograms to measure the mass of atoms and molecules? Because atoms and molecules are extremely small and it is very difficult to carry out calculations pertaining to them if the units are meant for macroscopic quantities.
 For find out the answer, we know that: Mass of one atom = 12 amu
\[1amu=\dfrac{\text{mass of 1 }{}_{6}^{12}C\text{ atom}}{12}\]
So, $1amu=\dfrac{(1.994\times {{10}^{-23}})kg}{12}$
Therefore, $1amu=1.662\times {{10}^{-24}}$g.

So, the correct answer is “Option D”.

Note: The answer to the question of why carbon is considered as the standard element is that because carbon can combine with other elements. Moreover, the Carbon-12 isotope is highly abundant in nature. Previously, Hydrogen and Oxygen are included as standards but scientists faced difficulties. After many years of arguing, scientists agreed that Carbon-12 would be the best unit of measurement for atomic masses.