In Table 7.5, the pattern that develops with increasing n suggests that the number of different sets ofl,mlvalues for a given energy level n isn2. Prove this mathematically by summing the allowed values ofmlfor a givenlover the allowed values oflfor a given n.

Short Answer

Expert verified

The number of different sets ofl,ml values for a given energy level n isn2 .

Step by step solution

01

 Given data

Energy level = n.

02

 Approach to find the final answer

For each n that is the principal quantum number, l, which is the azimuthal quantum number, can be from 0 to n – 1; for each n, there are 2l+1 allowed values ofml.

03

 To prove the number of different sets of l,ml values for a given energy level n is n2

Summing all the allowed values ofml for a given l over the allowed values of l for a given n as:

0n-12l+1=20+n-12n+n=n-1n+n=n2-n+n=n2

Thus, the number of different sets ofl,ml values for a given energy level n isn2 .

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Most popular questions from this chapter

Question: Explain to your friend. who has just learned about simple one-dimensional standing waves on a string fixed at its ends, why hydrogen's electron has only certain energies, and why, for some of those energies, the electron can still be in different states?

Classically, an orbiting charged particle radiates electromagnetic energy, and for an electron in atomic dimensions, it would lead to collapse in considerably less than the wink of an eye.

(a) By equating the centripetal and Coulomb forces, show that for a classical charge -e of mass m held in a circular orbit by its attraction to a fixed charge +e, the following relationship holds

ω=er-3/24πε0m.

(b) Electromagnetism tells us that a charge whose acceleration is a radiates power P=e2a2/6ε0c3. Show that this can also be expressed in terms of the orbit radius as P=e696π2ε03m2c3r4. Then calculate the energy lost per orbit in terms of r by multiplying the power by the period T=2π/ωand using the formula from part (a) to eliminate .

(c) In such a classical orbit, the total mechanical energy is half the potential energy, or Eorbit=-e28πε0r. Calculate the change in energy per change in r : dEorbit/dr. From this and the energy lost per obit from part (b), determine the change in per orbit and evaluate it for a typical orbit radius of 10-10m. Would the electron's radius change much in a single orbit?

(d) Argue that dividing dEorbit/dr by P and multiplying by dr gives the time required to change r by dr . Then, sum these times for all radii from rinitial to a final radius of 0. Evaluate your result for rinitial=10-10m. (One limitation of this estimate is that the electron would eventually be moving relativistically).

Calculate the electric dipole moment p and estimate the transition time for a hydrogen atom electron making an electric dipole transition from the to the (n,l,m)=(2,1,+1) ground state. Comment on the relationship of the result to that in Example 7.11.

What are the dimensions of the spherical harmonics Θl,ml(θ)Φml(ϕ)given in Table 7.3? What are the dimensions of theRn,l(r)given in Table 7.4, and why? What are the dimensions ofP(r), and why?

A hydrogen atom in an n = 2 state absorbs a photon,

  1. What should be the photon wavelength to cause the electron to jump to an n = 4 state?
  2. What wavelength photons might be emitted by the atom following this absorption?
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