Question

Write down the electronic configuration of (i) chlorine atom (ii) chlorine ion

Answer 1

Electronic configuration:

• It is the arrangement of electrons in the shells around the nucleus of an atom.
• The electrons are filled in the shells according to the increasing order of energy from the shell closest to the nucleus and moving outwards.

Chlorine (Cl) atom:

• Atomic number of Chlorine= 17
• In an atom, atomic number of Chlorine= Number of electrons= 17
• Chlorine has a total of 17 electrons
• Electronic configuration is 2,8,7 in neutral atom.
• First or the innermost shell can accommodates 2 electrons, second shell accommodates 8 electrons and third one accommodates 7 electrons of Chlorine atom.

Chlorine ion (Cl^-):

$$\begin{gathered} \mathrm{Cl}+{\mathrm{e}}^{-}\to {\mathrm{Cl}}^{-} \\ \left(\mathrm{Chlorine}\right)\left(\mathrm{electron}\right)(\mathrm{Chlorine}\mathrm{ion}) \end{gathered}$$

• As chlorine ion is formed by the gain of one electron, so the number of electrons in Chlorine ion or Chloride ion is 18.
• Therefore, electronic configuration of chlorine ion is 2,8,8.
• First or the innermost shell can accommodates 2 electrons, second shell accommodates 8 electrons and third one accommodates 8 electrons of Chlorine ion.