Question

Protactinium or Pa (Z = 91) =[Rn]5f26d17s2

Why we are writing [Rn]? Why 5f2 and Not 5f14?

Answer 1

We are writing [Rn] because it is a noble metal and has completly filled electronic configuration so instead of writing the long configuration we just write [Rn] Rn has atomic number 86 so after writing [Rn] we write atomic configuration after 86 here after 86 there is only 5 electrons which is tobe filled in the upcoming orbitals so we can't give 5f14