How would you write electronic configuration of scandium?

Hint: Knowing the atomic number of any element, we can easily determine the electronic configuration of them. Electronic configuration can be written in two forms i.e. by Bohr’s atomic theory and by Aufbau’s principle.

Complete answer:
Let us study the basic concepts while we determine the electronic configuration of the element;
In order to write the electronic configuration, we need to know the atomic number of an element; in short, we need to know the number of electrons present in total to divide them in accordance with the orbitals present in an atom.
By Bohr’s atomic theory, the electrons will be divided in the shells around the atom i.e. L, M, N, K. Whereas, by Aufbau’s principle and Hund’s rule the electrons are divided into the subshells as s, p, d, f (mostly accepted and used form).
Here, we know the atomic number of the element as 21 i.e. 21 electrons are present in the total which are to be divided into the shells of the element.
Those electrons can be divided as (Aufbau’s principle and Hund’s rule)-
The first two electrons will accommodate 1s orbital as its capacity is only to hold two electrons. Similarly, the next two electrons will go to 2s orbital. The following six electrons will move to 2p orbital as its capacity is to hold six electrons. Next, 3s will take two electrons and the remaining 6 electrons will go to 3p orbital.
Now, 3d and 4s orbitals are included in scandium. But 4s orbital have less energy than that of 3d thus, two electrons will firstly occupy 4s orbital and remaining one electron will move into 3d orbital.
Thus, the electronic configuration can be stated as $1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}3{{p}^{6}}4{{s}^{2}}3{{d}^{1}}$ .

Note:
The general electronic configuration for sulphur by the Bohr’s atomic theory can be stated as 2, 8, 9, 2 simply. Do note that the electronic configuration can also be stated including the noble gas element as; $\left[ Ar \right]4{{s}^{2}}3{{d}^{1}}$ .