Questions & Answers

Which symbol represents the unit of atomic mass, amu?
a.) u
b.) A
c.) M
d.) n

Answer Verified Verified
Hint: Atomic mass unit is also known as unified mass. This is represented by a small alphabetic letter, As we know that there are 26 alphabets in total, when numbered from a to z , this particular alphabet gets the number of 21.

Complete answer:
To find the symbol of atomic mass unit , we need to know what is this atomic mass unit mean by:
 The mass of an atom is called atomic mass. It is measured in terms of atomic mass unit (amu).
Atomic mass unit (amu) is the one -twelfth mass of Carbon - 12 isotopes. It is also known as unified atomic mass (u).
We can convert atomic mass unit (u) can be converted into gram by the following equation:
${ 1u=1.66\times { 10 }^{ -24 }g }$
For example, the mass of one atom of Carbon is 12 u.
Mass of one atom of Oxygen is 16 u
Mass of one atom of Chlorine is 35.5 u.
Therefore, ‘u’ symbol represents the unit of atomic mass, amu.
So, the correct answer is “Option A”.

Additional Information:
Now, we can go to a much broader concept, which is the mole concept.
Mole concept gives that 1 mole is defined as the mass of the avogadro number of particles (molecules).
Avogadro number is also represented as ${ N }_{ A }$.
${ 1{ N }_{ A }=6.022\times { 10 }^{ 23 } }$
Universally accepted value of avogadro number is ${ 6.022137\times { 10 }^{ 23 } }$.
So, there are seven significant figures in avogadro number.
For example, in 1 mol of ${ O }_{ 2 }$, there are ${ 2\times }$ Avogadro numbers of atoms.
In 1 mol of ${ H }_{ 2 }{ O }$ , there are ${ 3\times }$ Avogadro numbers of atoms.
Now, we can have a look at the term atomicity, which is given by the number of element atoms present in a molecule.
For Example: atomicity of ${ O }_{ 2 }$ is 2 , atomicity of ${ S }_{ 8 }$ is 8.

Note: Although we use the term atomic mass unit for the mass of atom but in the usual , we don’t use atomic mass unit as such, rather we will be converting into gram and will use the mass in grams. SI unit of mass is kg. And so, using gram is usually preferred, as it can be easily converted into SI (kg) as well.