Here in question no. 2.28  how is the mass no. taken to be 3 in the expression 

 

Mass of nucleus= A/ Avogadro no. By explaining this expression?

 

 

 

 

 

 

 

 

 

Mass of a nucleus is the ratio of mass number to the Avogadro's number. 

Now, this expression comes about because if we consider one nucleus, then its mass is given by the number of nucleons present in it. This will be given as the mass number A.

 

Now, one atom cannot be considered in real life. So, a standard volume of one mole is taken. In one mole there are Avogadro's number of atoms. Hence, if we want to calculate the mass of a single nucleus, we will divide the mass number by the Avogadro's number.

 

Also, note that the mass number is not taken as 3. The mass number A from the numerator and the denominator cancel each other out, and the denominator has a value 4/3. So, the 3 comes to the numerator.