Some practice test questions

  • Thread starter AznBoi
  • Start date
  • Tags
    Test
In summary: Anyway, back to my last question: How would you solve for E_1 if there E_1's on both sides of the equation? What do you substitute for the E_1 on the right side of the equation?In summary, AznBoi has a few practice test questions that they have gotten wrong and would like to know why. The first question involves the quantum transitions responsible for the sharp lines in an X-ray spectrum, with the correct answer being the inner electron shells instead of electron energy levels. The second question asks which quantities are conserved in all nuclear reactions, with the correct answer being electric charge and the number of protons. AznBoi also asks for an explanation on why charge is conserved and
  • #1
AznBoi
471
0
I have a few practice test questions that I have gotten wrong and would like to know why. (I have the answers, but not the explanations)

1. Quantum transitions that result in the characteristic sharp lines of the X ray spectrum always involve
a. the inner electron shells
b. electron energy levels that have the same principal quantum number
c. emission of beta particles from the nucleus
d. neutrons within the nucleus
e. protons within the nucleus

I put (b) for this answer because I thought the energy levels were related to the wavelength of the absorbed/emitted photons and spectrums depend on wavelength of radiation? Correct answer is (A)

2. Quantities that are conserved in all nuclear reactions include which of the following?
I. Electric charge
II. Number of nuclei
III. Number of protons

a. I only b. II only c. I and III only
d. II and III only e. I, II, and III

I picked (C) because I thought that both charge and protons (the atomic number Z) need to be conserved and must be equal on both sides of the reaction equation. Can someone please give me an explanation of why charge is conserved (I just heard it somewhere) and # of protons are not?
 
Physics news on Phys.org
  • #2
AznBoi said:
I have a few practice test questions that I have gotten wrong and would like to know why. (I have the answers, but not the explanations)

1. Quantum transitions that result in the characteristic sharp lines of the X ray spectrum always involve
a. the inner electron shells
b. electron energy levels that have the same principal quantum number
c. emission of beta particles from the nucleus
d. neutrons within the nucleus
e. protons within the nucleus

I put (b) for this answer because I thought the energy levels were related to the wavelength of the absorbed/emitted photons and spectrums depend on wavelength of radiation? Correct answer is (A)
Indeed, the wavelengths of the spectral lines do depend on the radiation wavelength. Consider the typical energy of an x-ray photon (10nm-0.01nm), now consider the difference in energy levels between the lower shells (n=1, n=2 etc). Do these energy levels get close together, or futher apart as n increases?
2. Quantities that are conserved in all nuclear reactions include which of the following?
I. Electric charge
II. Number of nuclei
III. Number of protons

a. I only b. II only c. I and III only
d. II and III only e. I, II, and III

I picked (C) because I thought that both charge and protons (the atomic number Z) need to be conserved and must be equal on both sides of the reaction equation. Can someone please give me an explanation of why charge is conserved (I just heard it somewhere) and # of protons are not?
Consider [itex]\beta[/itex] decay.
 
  • #3
Hootenanny said:
Indeed, the wavelengths of the spectral lines do depend on the radiation wavelength. Consider the typical energy of an x-ray photon (10nm-0.01nm), now consider the difference in energy levels between the lower shells (n=1, n=2 etc). Do these energy levels get close together, or futher apart as n increases?

Consider [itex]\beta[/itex] decay.

Don't the energy levels get closer together as n increases? I'm just using the energy level equation: [tex] E_{n}=\frac{Z^_{2}}{n^{2}}E{1}[/tex]

By the way, is E_1 always equal to -13.6V for any electron in any atom? I just need to know this ground level energy because only electrons move up and down energy level orbits right?
 
  • #4
By the way, is E_1 always equal to -13.6V for any electron in any atom?
No. Only for the hydrogen atom. E1 increases with Z.

The first ionization energy for He is 24.6 eV.

Ionziation energies of the outermost electrons or rather atoms/elements (which unfortunately are given in (kJ/mol).
http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/ionize.html

See - http://www.webelements.com/webelements/properties/text/image-line/e-binding-energy-k.html
http://www.webelements.com/webelements/properties/media/tables/line/e-binding-energy-k.gif

Somewhere there is an on-line resource with K and L series energies.

http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/xrayc.html
 
Last edited:
  • #5
Astronuc said:
No. Only for the hydrogen atom. E1 increases with Z.

The first ionization energy for He is 24.6 eV.

Ionziation energies of the outermost electrons or rather atoms/elements (which unfortunately are given in (kJ/mol).
http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/ionize.html

See - http://www.webelements.com/webelements/properties/text/image-line/e-binding-energy-k.html
http://www.webelements.com/webelements/properties/media/tables/line/e-binding-energy-k.gif

Somewhere there is an on-line resource with K and L series energies.

http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/xrayc.html
So if you have a different atom with a different number of protons then you'd have to find E_1 first by using [tex] E_{1}=Z^{2}E_{1} [/tex] right? How would you solve for E_{1} if there E_1's on both sides of the equation? What do you substitute for the E_1 on the right side of the equation?
 
  • #6
AznBoi, what I was getting at is x-ray photons have a relatively short wavelength and are therefore very energetic. This means that xray photons are only absorbed/emitted by electrons which undergo large energy level transitions. Since, as you correctly say the difference between the energy levels decreases as [itex]n\to\infty[/itex], xray photons are only absorbed/emitted by electrons at the lower energy levels (since [itex]\Delta E[/itex] is greatest here).

Does that make sense?
 

1. What is the purpose of practice test questions?

Practice test questions are designed to help individuals prepare for a specific exam or assessment. They allow individuals to become familiar with the types of questions that may be asked on the actual test and to assess their knowledge and skills in a simulated testing environment.

2. How can practice test questions benefit me?

Practice test questions can provide several benefits, such as helping individuals identify their strengths and weaknesses, familiarizing them with the format and structure of the actual test, and building their confidence and test-taking skills.

3. Are practice test questions similar to the actual test questions?

Practice test questions may be similar to the actual test questions in terms of content or format, but they are not exact replicas. The purpose of practice test questions is to provide individuals with a general idea of what to expect on the actual test and to help them prepare accordingly.

4. How many times should I take practice test questions?

The number of times an individual should take practice test questions may vary depending on their level of preparation and comfort with the material. It is recommended to take practice test questions multiple times to track progress and identify areas for improvement.

5. Can practice test questions guarantee success on the actual test?

While practice test questions can be a helpful study tool, they cannot guarantee success on the actual test. Other factors such as overall preparation, test-taking strategies, and time management also play a significant role in achieving a successful outcome on the actual test.

Similar threads

  • Introductory Physics Homework Help
Replies
4
Views
793
  • Introductory Physics Homework Help
Replies
22
Views
3K
  • Introductory Physics Homework Help
Replies
1
Views
744
  • Introductory Physics Homework Help
Replies
3
Views
987
  • Introductory Physics Homework Help
Replies
34
Views
1K
  • Introductory Physics Homework Help
Replies
5
Views
3K
  • Introductory Physics Homework Help
Replies
5
Views
899
  • Introductory Physics Homework Help
Replies
19
Views
923
  • Introductory Physics Homework Help
Replies
1
Views
689
  • Introductory Physics Homework Help
Replies
2
Views
1K
Back
Top