Question

The elements ${\text{Na}}$, ${\text{Mg}}$, ${\text{Al}}$, ${\text{Si}}$, ${\text{P}}$, ${\text{S}}$, ${\text{Cl}}$ and ${\text{Ar}}$ are arranged in the periodic table in the increasing order of their atomic numbers. Which element has the electronic configuration?
$1{s^2}\,2{s^2}\,2{p^6}\,3{s^2}\,3p_x^1\,3p_y^1\,3p_z^1$

Answer 1

Hint: The arrangement of electrons in the energy levels around the nucleus of an atom is known as the electronic configuration. The electrons fill up in the energy levels according to the Aufbau’s principle.

Complete step by step answer:
The elements ${\text{Na}}$, ${\text{Mg}}$, ${\text{Al}}$, ${\text{Si}}$, ${\text{P}}$, ${\text{S}}$, ${\text{Cl}}$ and ${\text{Ar}}$ are arranged in the period three of the periodic table in an increasing order of their atomic numbers.
The Aufbau’s principle states that in the ground state of the atoms, the orbitals are filled with electrons in order of the increasing energies. The order of energy of different orbitals in an atom is as follows:
$1s < 2s < 2p < 3s < 3p$ and so on.
The 3p orbital has three sub-orbitals $3{p_x}\,3{p_y}\,3{p_z}$.
The maximum number of electrons that can be accommodated is s-orbital are 2, p-orbital are 6.
The electronic configuration of the element is given to us. The electronic configuration is as follows:
$1{s^2}\,2{s^2}\,2{p^6}\,3{s^2}\,3p_x^1\,3p_y^1\,3p_z^1$
We have to count the total number of electrons. Thus,
Total number of electrons $ = 2 + 2 + 6 + 2 + 1 + 1 + 1 = 15$
Thus, the total number of electrons is 15.
The number of electrons is the atomic number of the element. Thus, we have to find the element with atomic number 15.
The element with atomic number 15 is phosphorous.
The chemical symbol for the element phosphorus is ${\text{P}}$.
Thus, the element with electronic configuration $1{s^2}\,2{s^2}\,2{p^6}\,3{s^2}\,3p_x^1\,3p_y^1\,3p_z^1$ is ${\text{P}}$.

Note:
The given elements are sodium $\left( {{\text{Na}}} \right)$, magnesium $\left( {{\text{Mg}}} \right)$, aluminium $\left( {{\text{Al}}} \right)$, silicon $\left( {{\text{Si}}} \right)$, phosphorous $\left( {\text{P}} \right)$, sulphur $\left( {\text{S}} \right)$, chlorine $\left( {{\text{Cl}}} \right)$ and argon $\left( {{\text{Ar}}} \right)$. The atomic number of sodium is 11, magnesium is 12, aluminium is 13, silicon is 14, phosphorus is 15, sulphur is 16, chlorine is 17 and argon is 18.