The part of the atom excluding the outermost shell is known as the ...... .

The volume of an atom is $10^5$ times the volume of its nucleus. If we consider the ratio of the radius of an atom to the radius of its nucleus,it is approximately $10^5$. Since volume $V = \frac{4}{3} \pi r^3$,the ratio of volumes is $(\frac{r_{atom}}{r_{nucleus}})^3 = (10^5)^3 = 10^{15}$. Therefore,the volume of an atom is $10^{15}$ times the volume of the nucleus. Choose the correct factor.

The radius of the nucleus is related to the mass number $A$ by

Radius of the nucleus is equal to $10^{-12} \ cm$ and that of the atom is equal to $10^{-8} \ cm$. What is the fraction of the volume of the atom occupied by the nucleus?

$A$ positron has a mass equal to that of a/an ...... .

Neutrons are found in atoms of all elements except in