Question

4d, 5p, 5f and 6p orbitals are arranged in the order of decreasing energy. The correct option is:

• A. 5f > 6p > 5p > 4d
• B. 6p > 5f > 5p > 4d
• C. 6p > 5f > 4d > 5p
• D. 5f > 6p > 4d > 5p

Answer 1

The Correct Option is A

To determine the order of decreasing energy levels of the orbitals mentioned (4d, 5p, 5f, and 6p), we use their principal quantum numbers (n) and azimuthal quantum numbers (l). The formula for energy levels is primarily dependent on the sum of n + l. If two orbitals have the same n + l value, the orbital with the lower principal quantum number (n) is considered to have lower energy. Here's how to calculate it:

1. 4d orbital:
   • Principal quantum number (n) = 4
   • Azimuthal quantum number (l) for d-orbital = 2
   • n + l = 4 + 2 = 6
2. 5p orbital:
   • Principal quantum number (n) = 5
   • Azimuthal quantum number (l) for p-orbital = 1
   • n + l = 5 + 1 = 6
3. 5f orbital:
   • Principal quantum number (n) = 5
   • Azimuthal quantum number (l) for f-orbital = 3
   • n + l = 5 + 3 = 8
4. 6p orbital:
   • Principal quantum number (n) = 6
   • Azimuthal quantum number (l) for p-orbital = 1
   • n + l = 6 + 1 = 7

Based on these calculations, the energy levels of the orbitals in decreasing order are:

• 5f (n + l = 8)
• 6p (n + l = 7)
• 5p (n + l = 6, n is lower than 4d)
• 4d (n + l = 6, n is higher than 5p)

Hence, the correct order of decreasing energy is: 5f > 6p > 5p > 4d.