Can some in solving these quantum mechanics problems

[anshul arora]

Homework Statement

ques 1 what is de-Broglie wavelength of a He-atom in a container at room temperature.
ques 2 calculate the number of exchange pairs of electrons present in configuration of Cu according to Aufbau Principle including d and s electrons.
ques 3 He atom can excited to 1s¹2p² by λ = 58.44nm. If lowest excited state for He lies 4857cm^- below the above. We need to calculate the energy for the lower excitation state.

Homework Equations

in the first question we can use de-Broglie wavelength,λ=h/mv but the problem is in finding the room temperature. is there any relation in finding velocity of an atom and temperature?
in third question we can use wavenumber = 1/λ, energy at nth orbit = -13.6z²/n²

The Attempt at a Solution

i have no idea how to solve question-2. is there any formula for calculating exchange pairs? and what actually is a exchange pair? please help me out

 

[Asim Riaz]

. for question-1, i think room temperature is 273 K and for He, mass is 4u. so the de-Broglie wavelength will be λ=h/mv λ= 6.62606876*10^-34/4*1.66053886*10^-27 *sqrt(3*8.314*273/4) λ= 1.35324*10^-10 m