Question

in which orbitals would the valence electrons for selenium (se) be placed?
s orbital and f orbital
s orbital only
s orbital and p orbital
d orbital only

Explanation:

Selenium (Se) has an atomic number of 34. Its electron configuration is $1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^4$. The valence electrons are in the outermost shell, which is the 4th shell here. The outermost shell has electrons in the 4s (s orbital) and 4p (p orbital) subshells. So the valence electrons of selenium are placed in s orbital and p orbital.

Answer:

s orbital and p orbital