Why is the 4s orbital lower in energy than the 3d orbital. I wonder if this is dialectal, or perhaps just individual.
Why is the 4s orbital lower in energy than the 3d orbital. Because of this, 4s orbitals are removed before 3d orbitals. This is why your teacher probably tells you that the rules (Aufbau principle) can be used up to calcium. The Aufbau principle predicts that the 4s orbital is always filled before the 3d orbitals, but this is actually not true for most elements! From Sc on, the 3d orbitals are actually lower in energy than the 4s orbital, which means that electrons enter the 3d orbitals first. In an atom with only one electron (Hydrogen) the 4s is not at lower energy than the 3d. Hence, electrons fill up in 4s before 3d orbital. The oddity is the position of the 3d orbitals, which are shown at a slightly higher level than the 4s. I stole this figure from Shriver & Atkins 5th ed: The red line represents the energy of the 3d orbital, and the blue line Jun 23, 2017 ยท 4s vs 3d – Which has the higher energy? Some of us may have learn this phrase “First In, First Out” or “FIFO” regarding 4s vs 3d. We don't say "Why we can grow taller?" so the construct should not be "Why we cannot grow taller?" The reason is that auxiliaries should come before the subject to make an interrogative. Relative why can be freely substituted with that, like any restrictive relative marker. The reversed order of the 3d and 4s orbitals only seems to apply to building the atom up in the first place. Now you know why: the 3d orbital doesn't always have more energy level than 4s. 8fry465h5yf87qdb4owffm0nhmu6olfrllil8