Is Sodium oxide (Na2O) ionic or covalent? Types of bond in Na2O
Sodium oxide is made up of two sodium and one oxygen atom having the chemical formula Na2O. It appears as a white solid and is used in glasses or ceramic. When water is added to sodium oxide then a compound is formed which is called sodium hydroxide.
In this article, we will discuss Is Sodium oxide (Na2O) ionic or covalent? Formation of bond in Na2O, etc.
So, Is Na2O ionic or covalent? Na2O is an ionic compound and consists of 2Na+ and O2- ions which are held together by ionic bonding. The bond formed between the metal (sodium) and nonmetal (oxygen) is ionic due to the large gap of electronegativity difference exists between them.
|Name of Molecule||Sodium Oxide|
|Molar mass||61.979 g/mol|
Why Sodium oxide (Na2O) is an ionic compound?
An ionic compound is a compound that is formed when the atoms lose or gain valence electrons to become more stable and form positive and negative ions.
Further, these charged ions are held by the electrostatic force of attraction, and eventually, a bond is formed between them which is called an ionic bond.
Usually, the metal atom transfers the electron whereas the nonmetal accepts the electrons.
Here, in the case of the Na2O compound, sodium is a metal atom that belongs to the alkali group and oxygen is a nonmetal that belongs to the p-block group.
So, sodium metal transfers its electrons whereas oxygen atom will accept it and a bond will form between them which is called an ionic bond.
As we see in the above figure, the sodium metal is transferring its electrons and oxygen as a nonmetal accepting the electrons, and both these formed 2Na+ and O2- ions which are held together by the electrostatic force of attraction, and an ionic bond forms between them.
Examples of some more ionic compounds – MgCl2, MgO, NaCl, etc.
How ionic bond is formed in Na2O?
An ionic bond is formed either by giving or taking electrons.
The formation of ionic bond in Na2O usually take three process-
(1). Formation of cation(2Na+)
A cation is formed when the metal atom loses its electron to obtains stability. In the case of Na2O, the sodium atom is a metal that belongs to group 1 in the periodic table and has an atomic number of 11.
The electronic configuration for sodium is 1s22s22p63s1 or [2, 8, 1]. So, by losing 1 electron, the sodium metal electronic configuration will be [2, 8]. So, now it has an electronic configuration close to the noble gas configuration and has 8 electrons in the outermost shell.
Hence, each sodium metal wants to lose 1 electron from its outermost shell to achieve stability.
(2). Formation of the anion(O2-)
An anion is formed when the nonmetal gains the electrons to obtains stability. In the case of the Na2O compound, oxygen is a nonmetal that belongs to group 16 in the periodic table and has an atomic number of 8.
The electronic configuration for oxygen is 1s22s22p4 or [2, 6]. So, by gaining 2 electrons, the oxygen nonmetal electronic configuration will be [2, 8]. So, now it has an electronic configuration close to the noble gas configuration and has 8 electrons in its outermost shell.
Hence, the oxygen nonmetal gains the 2 electrons to achieve the stable form.
(3). Electrostatic force attraction between ions(2Na+ and O2-)
Electrostatic force is non-contact force that attract the positive and negative charged particles or objects without touching them.
We know that opposite charges will always attract each other. So, the formation of ions 2Na+ and O2- will attract each other because of positive and negative charges.
Therefore, both these ions are linked together by the electrostatic force of attraction and a formation of a bond occurs between them which is called an ionic bond or electrovalent bond.
Why is Na2O not a covalent compound?
A covalent bond is formed when sharing of electrons is done between the atoms to achieve stability.
Usually, covalent bonds formed between the two nonmetals, between p-block and p-block, and formed when electronegativity difference between atoms exist less than 1.7.
Examples of some compounds that form covalent bonds – H2O, NH3, H2S, SO2, NO2, AlCl3, etc.
- Why does H2O form a covalent bond?
- Why does NH3 form a covalent bond?
- Why does H2S form a covalent bond?
- Why does SO2 form a covalent bond?
- Why does NO2 form a covalent bond?
- Why does AlCl3 form a covalent bond?
According to the Pauling scale of electronegativity-
- The covalent bond is formed between the two atoms when their electronegativity difference occurs less than 1.7.
- The ionic bond is formed between the two atoms when their electronegativity difference occurs more than 1.7.
Now check the electronegativity difference in Na2O compound-
⇒ The electronegativity value for sodium atom = 0.93
⇒ The electronegativity value for oxygen atom = 3.44
∴ The difference of the electronegativity between sodium and oxygen atoms = 2.51
So, the difference in electronegativity between sodium and oxygen is more than 1.7, hence, it is large enough to make an ionic bond between them as per the Pauling scale of electronegativity.
Also, in the Na2O compound, there is no sharing of electrons involves, sodium metal atom transfer its electrons and oxygen as nonmetal accept the electron to achieve stability by completing the octet.
And a bond is formed between the ions which is called an ionic bond.
Energy involving in the process of ionic bond formation in Na2O?
When a chemical bond is formed it releases energy, which helps to attain stability between the new bonds.
The formation of a bond releases the energy whereas the breaking of the bond absorbs the energy.
There are three types of energy involved in the process of ionic bond formation in Na2O.
(a). Ionization enthalpy
(b). Electron gain enthalpy
(c). Lattice energy
⇒ Ionization enthalpy
Ionization enthalpy is the amount of energy required to remove the loose electron of an isolated gaseous atom from its outermost shell, then convert it into a gaseous positive ion.
Ionization enthalpy is always positive and occurs when an electron loses from the atom.
So, in the case of ionic bond formation in Na2O, when an electron is loosed or released from the sodium metal then the energy associated with it is ionization enthalpy.
⇒ Electron gain enthalpy
This energy is just opposite to ionization energy. The electron gain enthalpy is the enthalpy that occurs when an electron is added to an isolated atom in the gaseous phase, then convert this isolated atom into a gaseous negative ion.
The electron gain enthalpy may be positive or negative but most of the time it is negative.
So, in the case of ionic bond formation in Na2O, when an electron is accepted or is added to the oxygen atom then energy associated with it is electron gain enthalpy.
⇒ Lattice energy
The lattice energy is the energy that releases when 1 mole of an ionic bond is formed from adding gaseous anion and cation.
The more the lattice energy releases during the formation of an ionic bond, the higher is the stability of that bond.
So, in the case of ionic bond formation in Na2O, when cation(2Na+) is attracted by anion(O2-), then some amount of energy is released which is called lattice energy.
As you see in the above figure when 2 moles of cation(2Na+) diffuses with one mole of the anion(O2-) then one mole of solid(Na2O) is formed.
And the energy released during the formation of ionic bonds in Na2O is lattice energy.
Properties of Sodium oxide
- It appears as white solid and odorless in nature.
- It has a boiling point of 1,950 °C and a melting point of 1,132 °C.
- It has a coordination geometry of tetrahedral for Na+ and cubic for O2-.
- When sodium oxide is added to water, it produces sodium hydroxide.
- It can react with ethanol and water.
Uses of Sodium oxide
- It is used in manufacturing glasses and ceramics.
- It is used in the industry of aerospace and advance electronics.
- It has good properties of ionic conductivity, hence, used for making the fuel cells.
- It is also used to create glazes that give exciting color responses.
Why does sodium metal lose electrons and oxygen gains the electron to form an ionic bond in Na2O?
This is because sodium is a metal that has low ionization energy, metals are more prone to lose electrons to achieve the octet.
As sodium metal has the electronic configuration (2, 8, 1), so, for sodium, it is easier to lose the one electron to achieve octet and hence, attains stability.
A nonmetal has high ionization energy and large electronegativity, they can easily accept the electrons to achieve the octet.
As oxygen nonmetal has the electronic configuration (2, 6), so, gaining two-electron makes its electron configuration (2, 8), hence, achieve the octet and attains stability.
Which has more covalent character Na2O or Li2O?
Both sodium and lithium belong to that same group and have the same valency with the same charge. But lithium is present just above sodium.
As we go down the periodic group, the atom size increases. Hence, sodium is larger than lithium.
Going by the trick to finding more covalent characters, use the C/S ratio formula.
⇒ C = Charge of cation
⇒ S = Size of the atom
“Larger is the C/S ratio, more will be the covalent character”.
So, both sodium and lithium have the same charge but the atomic size of sodium is larger than lithium.
Therefore, the C/S ratio of Li2O is larger than the C/S ratio of Na2O.
∴ The Li2O has a more covalent character than Na2O.
Which has more ionic character, Na2O or K2O?
Both sodium and potassium belong to the same group and have the same valency with the same charge.
“According to Fajan’s rule, the larger the size of the cation and the smaller the size of the anion favors ionic character in the molecule.”
So, here, neglect the size of the anion, as both Na2O and K2O have the same anion size.
Concentrate on the size of the cation. “The size of cation increase as we move down the group”.
The potassium metal is just presented below the sodium metal, hence, the size of potassium is larger than sodium.
Therefore, the K2O compound has an ionic character than Na2O.
- Is Sodium oxide (Na2O) ionic or covalent? Na2O is an ionic compound because the bond formed between sodium and the oxygen atom is ionic in nature, it is formed as each sodium atom loses one electron to form Na+ ion and oxygen atom accepts these electrons to form O2– ion, later these ions(2Na+ and O2-) are attracted by the electrostatic force of attraction and form the ionic bond.
- Na2O is ionic in nature but still, it has a covalent character also or you can say Na2O is not 100% ionic in nature.
- The difference in electronegativity between sodium(0.93) and oxygen(3.44) is 3.44–0.93=2.51 which is higher than 1.7, hence, according to the Pauling scale, the bond formed between sodium and an oxygen atom is ionic in nature.