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 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.
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.
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.)
Actinium is a trivalent metal; only in the actinium hydride is divalent.
Alkali metals
Actinium may be used in actinium-beryllium neutron sources or in radiotherapy.
Actinium is rarely used:- as actinium-beryllium neutron source- in radiotherapy