Question

a) An ion with mass number 37 possesses one unit of negative charge. If the ion contains 11.1% more neutrons than the electrons. Find the symbol of the ion.

b) An electron is in 3d orbitals. Give the possible values of n,l and $m_1$.

c) What is the maximum number of emission lines, When the excited electron of a $H$ atom in $n=6$ drops to the ground state?

Answer 1

Mass number $=37$

Number of proton $=x$ and No. of neutron $=y$

$x+y=\mathrm{37........1}$

No. of electron $=x+1$

$(x+1)+\frac{(x+1)\times 11.1}{100}=y$

$9x+9+x+1=9y$

$10x+10=9y$

$10x-9y=-10+$ ___ $2$

$9x+9y=37\times 9=333$

$10x-9y=-10$

$19x=323$

$x=\frac{323}{19}$ = $17$

$y=20$

Therefore, the symbol of ion ${Cl}^{-}$

$\left(b\right)$ electron in $9d$ orbital

$n=3,l=2,m=-2,-1,0,1,2$

$\left(c\right)$ No. of emission line $(n=6)$

$=\frac{n(n-1)}{2}$

$=\frac{6(6-1)}{2}=15$