Modern Physics

Bohr's Conclusions

Energy-level transitions, photons, and atomic spectra

Bohr's Conclusions lesson illustration

 

When an atom GAINS energy,
it is said to be an _______ state

 

 

Bohr's Conclusions lesson illustration

The Aurora Borealis, or Northern Lights,
shines above Bear Lake, Eielson Air Force Base, Alaska

gallery
(Full Image)

 United States Air Force photo by Senior Airman Joshua Strang

 

 

Fill In The Blank Notes

 

 

Think of an atom as a
 miniature solar system

Bohr's Conclusions lesson illustration

 

3 orbits are permitted
for this atom



1. Permitted orbits of an electron in an atom are limited

 

 

2. Each orbit is a different energy

 

 

3. Inside orbits have lower energies than the outside ones

 

 

4. When electrons in an atom change energy states they absorb or release energy

 

 

 


 Bohr's Conclusions lesson illustration Up energy level,Bohr's Conclusions lesson illustration

energy absorbed









Bohr's Conclusions lesson illustration Down energy level, Bohr's Conclusions lesson illustration

energy  released
  
as light

 

 

 

 

Permitted Orbital Energies
for Hydrogen

 

 

Reference table

 

Bohr's Conclusions lesson illustration 

 

 

 

 

Each orbital is associated with a specific energy

 

Energy
Level #

Energy

  

n = 3

-1.51 eV

 

Excited State

 

n = 2

-3.40 eV

 

Excited State

 

n = 1

-13.6 eV

Ground State
Lowest Energy Level

 

 

 

Electrons can only absorb or emit energy that is equal to the difference between the absolute value of 2 energy levels.

 

 

 

 

 

A single photon of energy is given off when electrons
go down energy levels.

 

 

Bohr's Conclusions lesson illustration

 

Check Your Understanding

5 quick questions — pick an answer to see if you’re right.

1. When an atom gains energy, its electron moves up and the atom is in…

2. Compared to outer orbits, inner orbits of an electron have…

3. A hydrogen electron drops from n = 3 (−1.51 eV) to n = 2 (−3.40 eV). What energy photon is emitted?

4. When an electron moves down an energy level, the atom…

5. The Northern Lights glow because electrons in atoms are…

NYSSLS Regents Practice · Modern Physics · Spectral Fingerprints

What Is the Star Made Of?

Astronomers pass starlight through a spectroscope. They see a continuous rainbow crossed by dark lines. The positions of the dark lines match the bright emission lines of hydrogen and helium measured in the laboratory.

What can astronomers conclude?

▶ Want a challenge? Open 6 more Regents-style questions  (harder · mixed formats)

Challenge score: 0 / 6

Select all that apply

C1. Place a check mark in two boxes to indicate statements that help explain why the starlight spectrum has dark lines.

Multiple choice

C2. Why are the dark absorption lines at exactly the same wavelengths as the element’s bright emission lines?

Substitute values

C3. One of helium’s dark lines in the starlight is at 5.88 × 10−7 m. Substitute numerical values into a mathematical representation that can be used to determine the energy of the photons absorbed by helium at this wavelength. Then calculate the energy. (h = 6.63 × 10−34 J·s; c = 3.00 × 108 m/s)

E = ( × 10−34 J·s)( × 108 m/s)( × 10−7 m) = × 10−19 J
Support or Refute · Justify

C4. A student makes the following claim.

Claim: If a star’s atmosphere contained sodium, its spectrum would show dark lines at the same wavelengths as the bright yellow lines of a sodium streetlight.

Place a check mark in either the Support or Refute box. Justify your response.

Multiple choice

C5. Helium was first discovered in the Sun’s spectrum before it was found on Earth. How?

Constructed response

C6. An astronomer wants to find out whether a distant star contains calcium. Describe how she could use laboratory measurements and the star’s spectrum to decide, and state what evidence would support the claim that the star contains calcium.

Bohr Model Examples →

Also see: The Big Bang — evidence for the origin of the universe

Also see: Nuclear Physics — radioactive decay, fission, and fusion