Question

What is the ground state electron configuration of ${O^2}$ ion?

Answer 1

The distribution of electrons in an element's atomic orbitals is described by its electron configuration. Atomic electron configurations are represented by a standard notation in which all electron-containing atomic subshells (with their number of electrons stated in superscript) are arranged in a sequential order.

Complete answer:
The term "ground-state" refers to an element's lowest energy state (not in an excited state). The term "neutral oxygen" refers to an atom that has no charge, implying that no electrons have been removed or added.
The number of oxygen electrons $= 8$
Here Oxygen gained $2$ electrons and formed ${O^{2 - }}$ .
Therefore, the electrons in ${O^{2 - }}$ will be $8 + 2 = 10$ .
Electronic arrangement can be written as $1{s^2}2{s^2}2{p^6}$ .
Hence, the ground state electron configuration of ${O^2}$ ion is $1{s^2}2{s^2}2{p^6}$ .

Additional Information:
The Hund’s rule specifies the order in which electrons are filled in all of a subshell's orbitals. It states that before a second electron is filled in an orbital, every orbital in a particular subshell is single-occupied by electrons. The electrons in orbitals with only one electron have the same spin in order to maximise the total spin (or the same values of the spin quantum number).

Note:
On the other hand, standard notation usually results in extended electron configurations (especially for elements having a relatively large atomic number). In some cases, a shortened or condensed notation may be used instead of the standard notation. In the abbreviated notation, the series of completely full subshells that correspond to a noble gas's electron configuration are replaced by the noble gas's symbol in square brackets.