Question

What is the number of valence electron in:
A. Sodium ion($N{a}^{+}$)
B. Oxide ion($O^{2-}$)
(Atomic no of Na=11, O=8)

Answer 1

Hint: We need to grasp the electronic configuration of sodium and oxygen atoms in state to resolve the question.
Electronic configuration, also called electronic structure, is the arrangement of electrons in energy levels around an atomic nucleus. In terms of a more refined, quantum-mechanical model, the K–Q shells are subdivided into a group of orbitals, each of which may be occupied by a pair of electrons.

Complete answer:
Each shell can contain only a set number of electrons: the primary shell can setback to 2 electrons, the second shell can delay to eight (2 + 6) electrons, the third shell can interruption to 18 (2 + 6 + 10) electrons then on the overall formula is that the nth shell can carry upto to $2n^2$ no of electrons.
The symbols used for writing the electron configuration start with the shell number (n) followed by the sort of orbital and at last the superscript indicates what number electrons are within the orbital. For instance: gazing at the table, you'll see that Oxygen has 8 electrons.
There are 4 shells denoted by K,L,M, and N.
In nuclear physics and quantum chemistry, the electron configuration is the distribution of electrons of an atom or molecule (or other physical structure) in atomic or molecular orbitals. For example, the electron configuration of the neon atom is $1s^{2}2s^{2}2p^6$, using the notation.
Similarly the electronic configuration of sodium atom is $1s^{2}2s^{2}2p^{6}3s^1$Now if we remove one electron from its valence shell the it's configuration are going to be $1s^{2}2s^{2}2p^6$.
Therefore from the above configuration we will conclude no of electrons in Na+ is eight.
Now the electronic configuration of O is $1s^{2}2s^{2}2p^4$.
Now in oxide ion oxygen gains 2 electrons therefore it's configuration becomes $1s^{2}2s^{2}2p^6$.
Therefore from the above configuration we are able to conclude that the entire number of valence electrons in oxide ions is 10.

Note:
Sodium ion and oxide ion are stable ions because they need attained stable configuration by completing their outer orbitals . That they need full filled p orbital in both the cases and have attained the closest element configuration.