# which orbital has lower energy 4d or 5f

Dear Student,

According to Aufbau Principle, which is also known as n+l rule. The n+l value of the above given orbitals are:
• 4d:
n = 4
l = 2
n + l = 6
• 5f:
n = 5
l = 3
n + l = 8

Now, as we can see that n + l value of 4d-orbital is less so it will have a lower energy than 5d-orbital and thus electrons will firstly be filled in 4d-orbital then in 5f-orbital (according to Aufbau Principle).