Question

Among the following quantities:
(i) mass number
(ii) average mass of a Carbon atom in amu
(iii) the charge of nucleus in amu and
(iv) mass of a Carbon -12 atom in grams

• A. only (i) is whole number
• B. only (i) and (iii) are whole number
• C. only (i) and (iv) are whole numbers
• D. only (iii) and (iv) are whole numbers

Answer 1

The correct option is B only (i) and (iii) are whole number

(1) The mass number is always the whole number because the mass number is the total number of neutrons and protons in the nucleus of the atom and an atom never contains fractional or an integer number of protons or neutrons.

(2) Average mass of carbon atom in $amu$ is $12.011u$. It is in decimal and can be written as fractional form.

(3) Charge on the nucleus in $amu$:- Charge on the nucleus is equal to the number of protons and the number of protons are always whole.

(4) Mass of carbon atom= $\frac{Massofcarbon}{Avogadronumber}$

$=\frac{12g}{6.022\times {10}^{23}}$

$=1.99\times {10}^{-23}$ grams

It is not a whole number.