In which orbitals are the valence electrons of selenium (Se) located?

• A. 3d and 4s
• B. 3p and 3d
• C. 4d and 4f
• D. 4s and 4p

Answer: (D)

Verified step by step guidance

1. Identify the atomic number of selenium (Se), which is 34, to understand its electron configuration.
2. Write the full electron configuration of selenium by filling orbitals in order of increasing energy: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, etc.
3. Determine the valence shell by looking at the highest principal quantum number (n) occupied by electrons; for selenium, this is n = 4.
4. Identify the orbitals in the valence shell (n=4) that contain electrons; these are the 4s and 4p orbitals.
5. Conclude that the valence electrons of selenium are located in the 4s and 4p orbitals, not in 3d, 4d, or 4f orbitals.