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Out of 3d and 4s orbitals, which is filled first ? |
Answer» 4s orbital is filled first because it has lower energy. The energies of the orbitals can be compared by their n + l values. For 4s orbital, n +l(4 + 0) value is 4 while for 3d orbital, n + l (3 + 3) value is 5. Therefore 4s orbital is filled before 3d orbital. However, this is true only for multielectron atom. In the excited states of one electron species `(H, He^(+), Li^(2+))`, 3d orbital will be filled before 4s orbital. | |