Question

What is the electron configuration of an element with atomic number 109?

Answer 1

Hint :The atomic number represents the number of electrons in an atom of the element. Using any principle to fill atomic orbitals, you can find the electronic configuration of the given element.

Complete Step By Step Answer:
The electronic configuration of the required element is $ \left[ Rn \right]5{{f}^{14}}6{{d}^{7}}7{{s}^{2}} $ .
Let us see how the electronic configuration of any element can be determined by some principles. Let us take aufbau’s principle here.
The aufbau’s principle states that the electrons will occupy lower energy orbitals before filling the higher energy orbitals. Thus, electrons will first occupy the lower energy orbitals and after they are completely filled, then they will try and occupy the comparatively higher energy orbitals.
Let us know now, how the notation works.
Each and every atom has shells where the electron can reside in that atom. There are a total of four shells named K, L, M, and N. In the first shell, only two electrons can adjust, in the second only eight, in the third only eighteen and in the fourth only thirty two.
Thus, as lower energy orbitals are filled first, K shell is filled first then L and so on.
The shells have subshells, K has 1s, L has 2s and 2p, M has 3s, 3p and 3d and N has 4s, 4p, 4d, and 4f.
These subshells can accommodate 2, 6, 10 and 14 electrons in themselves respectively.
Now, as hydrogen only has one electron in its atoms, the electronic configuration of hydrogen becomes, $ 1{{s}^{1}} $ , as oxygen has 8 electrons in its atoms, the electronic configuration of oxygen becomes, $ 1{{s}^{2}}2{{p}^{6}} $ and this is how you can find the electronic configuration of element with given atomic number.
The electronic configuration of the required element has been written as $ \left[ Rn \right]5{{f}^{14}}6{{d}^{7}}7{{s}^{2}} $ , because the electron configuration of this element before $ 5{{f}^{14}}6{{d}^{7}}7{{s}^{2}} $ is same as that of radon (Rn).

Note :
You don’t have to use only aufbau’s principle, you can use other principles too to find out the electronic configuration of any element. Whenever any electronic configuration is the same as that of any inert gas, you don’t have to write the whole electronic configuration, you can write it like it has been given in the answer.