(a) How many subshells are associated with$\mathrm{n}=4$ ? (b) How many electrons will be present in the subshells having ${\mathrm{m}}_{\mathrm{s}}$ value of $-1/2$ for $\mathrm{n}=4$ ?

Find (a) the total number and (b) the total mass of neutrons in $7 \mathrm{mg} \mathrm{of}$ ${}^{14}\mathrm{C}$. 

(Assume that mass of a neutron= $1.675\times {10}^{-27} \mathrm{kg}$)

How many neutrons and protons are there in the following nuclei ?

${}_6{}^{13}\mathrm{C}, {}_8{}^{16}\mathrm{O}, {}_{12}{}^{24}\mathrm{Mg}, {}_{26}{}^{56}\mathrm{Fe}, {}_{38}{}^{88}\mathrm{Sr}$

Write the complete symbol for the atom with the given atomic number (Z) and atomic mass (A)

$\mathrm{Z}=92 , \mathrm{A}=233.$

Write the complete symbol for the atom with the given atomic number (Z) and atomic mass (A)