Question

The electronic configuration of silicon is \\_\\_\\_\\_\\_\\_\\_ and that of sulphur is \\_\\_\\_\\_\\_\\_\\_.
(i) Silicon $- \,\,2,\,8\,,\,1$; Sulphur $- \,\,2,\,8,\,8$
(ii) Silicon $- \,\,2,\,8\,,\,4$; Sulphur $- \,\,2,\,8,\,3$
(iii) Silicon $- \,\,2,\,8\,,\,2$; Sulphur $- \,\,2,\,8,\,6$
(iv) Silicon $- \,\,2,\,8\,,\,4$; Sulphur $- \,\,2,\,8,\,6$

Answer 1

Electronic configuration is the arrangement of electrons in energy levels around an atomic nucleus. The energy levels are filled following Aufbau’s Principle which states that in the ground state of an atom or ion, electrons fill atomic orbitals of the lowest available energy levels before occupying higher levels.

Complete step-by-step answer: The electron configuration is the distribution of electrons of an atom in energy levels around the nucleus of the atom.
An electron shell described the set of allowed states or energies that share the same principal quantum number $n$ , that electrons may occupy. An atom's ${n^{th}}$ electron shell can accommodate $2{n^2}$ electrons, e.g. the first shell can accommodate two electrons, the second shell eight electrons, the third shell can accommodate up to eighteen electrons and so on.
The shells further consists of subshells which are defined by the azimuthal quantum number$l$. The value of $l$ ranges from $0$ to $\left( {n - 1} \right)$. The values $l\, = \,0,\,1\,,\,2,\,3$ correspond to the $s,\,p,\,d$and $f$labels, respectively having energies $s < p < d < f$. The maximum number of electrons that can be placed in a subshell is given by $2\left( {2l + 1} \right)$. This gives two electrons in $s$ subshell, six electrons in $p$ subshell, ten electrons in $d$ subshell and fourteen electrons in $f$ subshell.
Electrons are filled following Aufbau’s Principle which states that in the ground state of an atom or ion, electrons fill atomic orbitals of the lowest available energy levels before occupying higher levels, hence following the order: $1s,\,2s,\,2p,\,3s,\,3p,\,4s,\,3d,\,4p,\,5s,......$as orbitals with a lower $\left( {n + l} \right)$value are filled before those with higher $\left( {n + l} \right)$ values. In the case of equal $\left( {n + l} \right)$values, the orbital with a lower $n$ value is filled first.
Silicon has an atomic number of $14$, hence its electronic configuration can be written as $1{s^2}\,2{s^2}\,2{p^6}\,3{s^2}\,3{p^2}$ i.e. $2,\,8,\,4$.
Sulphur has an atomic number of $16$, hence its electronic configuration can be written as $1{s^2}\,2{s^2}\,2{p^6}\,3{s^2}\,3{p^4}$ i.e. $2,\,8,\,6$.

Hence the correct answer is (iv) Silicon $- \,\,2,\,8\,,\,4$; Sulphur $- \,\,2,\,8,\,6$.

Note: For this kind of question you must have a good knowledge of the placement of different elements in the periodic table. If you know the periodic table you will know the atomic number of the particular element and hence can easily determine the electronic configuration of the element.