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Show the formation of Na2O and MgO by the transfer of electrons.

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Formation of Na2O : 
The atomic number of sodium is 11 and it has only one valence electron. 

Hence, electronic configuration of 11Na is 2, 8, 1.

The atomic number of oxygen is 8 and it has 6 electrons in its valence shell. 

Hence, electronic configuration of 8O is 2, 6. 

Sodium has a tendency to lose the valence electron and oxygen has a tendency to gain the electron lost by sodium. Since sodium can lose only one electron of the valence shell and oxygen atom needs two electrons to complete its octet in the valence shell, two atoms of sodium combine with one atom of oxygen. By losing valence electron, sodium is changed into Na+ and by gaining two electrons lost by two sodium atoms, oxygen atom is changed into an oxide anion, O2-. In this process, both the atoms, sodium and oxygen, obtain the stable electronic configuration of the noble gas neon.

\(\underset{2,8,1}{Na} \longrightarrow \underset{2,8}{Na^+}+e^-\)

\(\underset{2, 6}{O}+2e^-\longrightarrow \underset{2,8}{O}^{2-}\)

\(2Na^++O^{2-}\longrightarrow\) \(2Na^+O^{2-}\) or \(Na_2O\)

The oppositely charged sodium ion, Na+ and oxide ion, O2- are now held together by electrostatic forces of attraction or by ionic or electrovalent bond. Na2O is, therefore, an ionic or electrovalent compound.

Formation of MgO: 

The atomic number of magnesium = 12

Its electronic configuration is 


It has two electrons in its outermost shell. So, the magnesium atom donates its 2 valence electrons and forms a stable magnesium ion, Mg2+ to attain the electronic arrangement of neon gas.

\(\underset{2,8,2}{Mg}\longrightarrow \underset{2,8}{Mg^{2+}}+2e^-\)

The atomic number of oxygen = 8

Electronic configuration = 

\(\begin{matrix}K & L\\2,&6\end{matrix}\)

It has six electrons in its valence shell. Therefore, it requires two more electrons to attain the stable electronic arrangement of neon gas. Thus, oxygen accepts two electrons donated by magnesium atom and forms a stable oxide ion, O2-.

\(\underset{2,6}{O}+2e^-\longrightarrow \underset{2,8}{O^{2-}}\)

The oppositely changed magnesium ions, Mg2+ and oxide ions,O2-, are held together by a  strong force of electrostatic attraction to form Magnesium oxide compound Mg2+O2- or MgO.

MgO is an ionic compound. 

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Atomic number of sodium - 11

Electronic configuration of sodium - 1s22s22p63s1

It has one valence electron, it will lose one electron to get octet configuration 

Atomic number of oxygen - 8

Electronic configuration of oxygen - 1s22s22p4

It is two electrons short of octet configuration, thus it will gain two electrons.

During the bond formation between sodium and oxygen, two sodium atoms loses one electron each to oxygen atom,

2Na – 2e → 2Na+

O + 2e–  → O– 2

2Na+ + O– 2 → Na2O

Atomic number of Magnesium - 12

Electronic configuration of Magnesium -1s22s22p63s2

It has two valence electrons , it will lose two electrons to get octet configuration

Atomic number of oxygen -8

Electronic configuration of oxygen −1s22s22p4 

It is two electrons short octet configuration, thus it will gain two electrons.

During the bond formation between Magnesium and Oxygen, one magnesium atom loses two electrons to oxygen atom.

Mg –  2e → Mg2+

O + 2e → O–2

Mg+2 + O–2 → MgO

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