Question

Explain how the electrons are arranged in the shells of Potassium atom.

Answer 1

• The arrangement of electrons in various shells of an atom of an element is called electronic configuration.
• The electrons can be accommodated into a particular energy shell as given by the formulae $2{\mathrm{n}}^2$, where $\mathrm{n}$ is the number of the shell or orbit.
• The outermost shell of an atom is called the valence shell, which cannot accommodate more than 8 electrons even though it has the capacity to hold more electrons.
• It means the outermost shell of every atom holds a maximum of 8 electrons except 1 st shell(K shell) which can hold only 2 electrons.
• The chemical symbol of Potassium = $\mathrm{K}$
• The atomic number of Potassium $=19$
• Number of protons = Atomic number$\left(\mathrm{Z}\right)=19$
• Number of electrons = Number of protons $=19$
• First shell or K shell ($\mathrm{n}=1$) can accommodate the number of electrons = $2\times 1^2=2$
• Second shell or L shell ($\mathrm{n}=2$) can accommodate the number of electrons = $2\times 2^2=2\times 4=8$
• As per the formulae remaining 9 electrons occupy the third shell or M shell ($\mathrm{n}=3$) which can hold up to the maximum of 18 electrons( $2\times 3^2=2\times 9=18$)
• But we know that the outermost shell of an atom is called the valence shell, which cannot accommodate more than 8 electrons even though it has the capacity to hold more electrons.
• Therefore M shell accommodates 8 electrons and the fourth shell or N shell (n=4$\mathrm{n}=4$) accommodates only $1$ electron.
• Hence the electronic configuration of Potassium ($\mathrm{K}$) = $$\begin{gathered} \mathrm{K}\mathrm{L}\mathrm{M}\mathrm{N} \\ 2881 \end{gathered}$$