Atom Structure Models

Step 1: Concept
Spectral series are named based on the lower energy level ( ) the electron drops to.
Step 2: Analysis
Lyman ( ), Balmer ( ), Paschen ( ), etc.
Step 3: Conclusion
Since the transition ends at , it belongs to the Balmer series.
Final Answer: (B)

Step 1: Inductive Effect
Aliphatic amines are generally more basic than ammonia ( ) because alkyl groups push electrons (+I effect) toward the nitrogen.
Step 2: Solvation Effect
In aqueous medium, basicity is influenced by solvation. Tertiary amines are less basic than secondary/primary amines because their large cations are poorly solvated by water.
Step 3: Final Order
Combining these effects, the increasing order for methyl amines is: .
Final Answer: (b)

Step 1: Use Bohr’s formula for electron velocity.
The velocity of an electron in a particular orbit is inversely proportional to the square root of the principal quantum number , i.e.,

Step 2: Calculate the velocity ratio.
For the second orbit ( ) and the fifth orbit ( ), the ratio of velocities is:

Step 3: Conclusion.
Thus, the velocity of the electron in the fifth orbit is .

Step 1: Understanding the Concept:
Threshold wavelength: . J s, eV = J.
Step 2: Detailed Explanation:
J.
m = 1808 Å ≈ 1800 Å.
Alternatively: Å.
Step 3: Final Answer:
Thus, threshold wavelength = 1800 Å.

Concept: Energy levels of hydrogen:

Step 1: Ground state energy

Step 2: Check excitation level Given photon energy

Step 3: Possible transitions From , electron can undergo:

Step 4: Number of spectral lines Conclusion

Concept: Rydberg formula:

Step 1:Absorption spectrum Electron absorbs energy and moves from lower to higher level. For absorption (Balmer limit), lowest level involved is:

Step 2:Shortest wavelength Shortest wavelength maximum wave number

Step 3:Substitute

Step 4:Final value Conclusion: