Actinium is in period 7, group 3A : so 7s2 is the highest sublevel of this first 5f-block element the actinides (89-103).
The highest sublevel that Promethium can have is 4f. It is possible for 14 electrons to be placed around Promethium, since the elements in this sublevel each have 7 orbitals.
The highest energy sublevel for tellurium (Te), which has an atomic number of 52, is the 5p sublevel. In its electron configuration, tellurium is represented as [Kr] 5s² 4d¹⁰ 5p⁴, indicating that the 5p sublevel is the outermost and highest energy level occupied by electrons.
The next highest energy atomic sublevel after 4p is the 5s sublevel. In the electron configuration of an atom, energy levels increase with increasing principal quantum number (n), so the 5s sublevel is higher in energy than the 4p sublevel.
It is the f sublevel. Uranium has the configuration [Rn] 5f3 6d1 7s2.
In uranium 238, the highest sublevel electron occupies is the 5f sublevel. Uranium has 92 electrons, so filling up the electron configuration involves reaching the 5f sublevel before completing the entire orbital diagram.
Iron (Fe) has an atomic number of 26. In terms of electron configuration, its sublevel notation is 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁶. This indicates that iron has two electrons in the 4s sublevel and six electrons in the 3d sublevel, with the 3d sublevel being the highest energy level that is partially filled.
The F-Sub level
One electron occupies the highest energy sublevel of alkali metals. Alkali metals have one electron in their outermost energy level, making them highly reactive.
This description fits elements in the lanthanide and actinide series of the periodic table. These elements have their highest occupied s sublevel and a nearby f sublevel containing electrons due to the electron configurations in their atoms.
The heaviest known atom is Oganesson (Og), which has an atomic number of 118. In the context of electron configuration, the p sublevel can hold a maximum of six electrons and is present in elements from groups 13 to 18. For Oganesson, the highest occupied p sublevel is the 6p sublevel, which can contain up to six electrons, but it is only partially filled in this element. Thus, while Oganesson has a 6p sublevel, the number of electrons in this sublevel is subject to ongoing research and may not be fully determined.
There are 9 orbitals in a g sublevel. (there is 1 in an s sublevel, 3 in a p sublevel, 5 in a d sublevel, 7 in an f sublevel, 9 in a g sublevel, 11 in an h sublevel, etc.)
Lets take the Lanthanides as an example. Lanthanum has its 5d sublevel filled before its 4f, even though the 4f is lower in energy and should, by the Aufbau Principle, be filled first. However, this is an exception because it happens to be the most stable configuration. It has one electron in the 5d sublevel and none in the 4f, and since it has no "f" electrons, it cannot be part of the f-bar's upper row (the Lanthanide series). The Lanthanides themselves will each also have one electron in the 5d sublevel, and the first element will also have one in the 4f sublevel. This trend will continue for all 14, and thus the 4f sublevel is filled. Hafnium, the element immediately after the last Lanthanide, will resume filling the 5d sublevel as normal, with two electrons in it and a completely filled 4f sublevel. The anomaly does not really change much; after all, if the valence electron in Lanthanum were not in the 5d sublevel and instead in the 4f, it would start off the Lanthanide series, there would be 14, and it would simply end one element before it normally does. The numbers all add up, in any case, and this is the natural order of things. For Actinides, replace the word Lanthanum with Actinium, Hafnium with Darmstadtium, 5d with 6d, and 4f with 5f. Everything works out perfectly; all the confusion is just caused by the stubborn little electron who doesn't want to be the first f-block element (and so he moves up into 5d, and stays there while the others take their appropiate places, which are moved one up thanks to his desire to maintain stability).