Similar to electron diffraction, neutron diffraction microscope is also used for the determination of the structure of molecules. If the wavelength used here is $800 \mathrm{pm}$, Calculate the characteristic velocity associated with the neutron.

The quantum numbers of six electrons are given below. Arrange them in order of increasing energies. If any of these combination(s) has/have the same energy lists:

1. $\mathrm{n}=4, \mathrm{l}=2, {\mathrm{m}}_{\mathrm{l}}=–2, {\mathrm{m}}_{\mathrm{s}}=–1/2$
2. $\mathrm{n}=3, \mathrm{l}=2, {\mathrm{m}}_{\mathrm{l}}=1, {\mathrm{m}}_{\mathrm{s}}=+1/2$
3. $\mathrm{n}=4, \mathrm{l}=1, {\mathrm{m}}_{\mathrm{l}}=0, {\mathrm{m}}_{\mathrm{s}}=+1/2$
4. $\mathrm{n}=3, \mathrm{l}=2, {\mathrm{m}}_{\mathrm{l}}=–2, {\mathrm{m}}_{\mathrm{s}}=–1/2$
5. $\mathrm{n}=3, \mathrm{l}=1, {\mathrm{m}}_{\mathrm{l}}=–1, {\mathrm{m}}_{\mathrm{s}}=+1/2$
6. $\mathrm{n}=4, \mathrm{l}=1, {\mathrm{m}}_{\mathrm{l}}=0, {\mathrm{m}}_{\mathrm{s}}=+1/2$

 Indicate the number of unpaired electrons in: (a) $\mathrm{P}$, (b) $\mathrm{Si}$, (c) $\mathrm{Cr}$, (d) $\mathrm{Fe}$, (e) and $\mathrm{Kr}$.