Question

Write the electronic configuration of scandium and aluminium.

Answer 1

Hint: Electronic configuration can be written only if we know the atomic number of the elements because the atomic number gives us the number of electrons of the atoms. Aluminium has an atomic number of 13 and scandium has atomic number of 21.

Complete step by step solution:
-Electronic configuration represents the number of electrons assigned to each orbital, subshell and shell of an atom. There are many rules that govern the electron filling in the atom. All the rules and the number of total electrons help in writing the electronic configuration of an atom.
-After studying about the orbitals, rules were made so as to fill the electrons in those orbitals. Aufbau stated a law after certain experiments. There were 3 rules for electronic configuration.
1. (n+l) rule – It tells us in which subshell the electron goes first. Electrons enter in that subshell first which has the least value of n+l. This is because that subshell has the lowest energy level.
2. Hund’s rule of maximum multiplicity – Electrons are placed so as to obtain maximum multiplicity which is obtained by putting electrons of the same spin in different orbitals.
3. Pauli’s exclusion principle – It stated that no 2 electrons can exist with all 4 same quantum numbers.
-Following all these rules, we can write the electronic configuration of both the elements. For aluminium, the configuration is $1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}3{{p}^{1}}$
Configuration for scandium is $1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}3{{p}^{6}}3{{d}^{1}}4{{s}^{2}}$


Note: : Many elements do not follow this law and so their configuration is different from that depicted by the law. Lanthanoid and actinoid series do not follow this law. Also elements like Nb, Cu, Cr, Mo, Tc, Ru, Rh, Pd, Ag, Au, Pt do not follow this law.