Hydrogen fluoride is composed of a hydrogen atom and a fluorine atom having a chemical formula as HF. The molecular weight of hydrogen fluoride is 20.01 g/mol.
Hydrogen fluoride is a gas or liquid which is colorless and has an irritating odor. The aqueous form of hydrogen fluoride is called hydrofluoric acid.
It is an essential feedstock in preparing several vital compounds, which include pharmaceuticals and polymers.
Hydrogen fluoride is a hazardous gas and forms corrosive hydrofluoric acid with moisture.
The gas can additionally lead to blindness by the quick dissolution of the corneas, thus stored in cylinders.
Let us explore if HF is a covalent or ionic compound in this article.
So, is HF ionic or covalent? Hydrogen fluoride is a covalently bonded polar molecule because of the unequal sharing of electrons among more electronegative fluorine and the less electronegative hydrogen atom. The electronegativity difference between hydrogen and fluoride is 1.78 and is considered polar covalent because fluorine is bonded to non-metallic hydrogen.
Let us now understand the concept of covalent bonding and ionic bonding.
What is a Covalent Bond?
A covalent bond involves the sharing electron pairs among participating atoms.
The bonding results from the electrostatic force of attraction of their nuclei to the electrons. It can hold the atoms collectively.
The atoms share electrons to achieve a stable electronic configuration considering the octet rule.
Compounds that show covalent bonds are recognized as covalent compounds. Covalent bonds are further termed molecular bonds and are most common in organic chemistry than ionic bonds.
Formation of Covalent Bonds
A covalent bond formation occurs if the electronegativity difference among the participating atoms is significantly less.
Electronegativity is termed as the capacity of an atom to pull electrons towards itself. The atoms covalently bond with the other participating atoms to achieve higher stability, which can be obtained by sharing the valence electrons and making a complete valence shell.
Covalent bonds bind the different atoms collectively as the electrostatic attraction among the positively charged nuclei, and the negatively charged electrons are more significant as compared to the repulsion among the identical charged nuclei.
As a result, this attraction thereby stabilizes the molecules.
The intensity of a covalent bond is defined by the force needed for breaking the bond, which means the total energy required to divide the covalently bonded atoms.
Different types of Covalent Bond
A covalent bond is organized based on the number of shared electrons pair, the bond polarity, and the coordination of the atoms.
The covalent bonds are classified into three types of bonds depending on the shared electron pairs.
1. Single Covalent Bond
When a pair of electrons or a total of 2 electrons are shared among the atoms, it forms a single covalent bond, also identified as simply a single bond.
2. Double Covalent bond
When 2 electron pairs or a total of 4 electrons are shared among the atoms it forms a double covalent bond, also identified as a simple double bond.
3. Triple Covalent Bond
When 3 electron pairs or a total of 6 electrons are shared among the atoms it forms a triple covalent bond, also identified as a simple triple bond.
Depending on the polarity of the bond and the coordination of the atoms, covalent bonds are classified into three categories:
1. Polar Covalent Bond
A polar covalent bond formation occurs if the sharing atoms possess a notable difference in the electronegativities.
For polar covalent bonds, the electronegativity difference lies in the range between 0.1 to 2.
Thus, the bonded electron pair is pulled toward the higher electronegative atom, making the atom somewhat negative, and the opposite atom becomes slightly positive.
When the bond is a polar covalent bond, the sharing of electrons between the atoms is unequal, as they are greatly pulled to one nucleus as compared to the other.
Further, the atom that pulls the electrons in its direction with a greater influence is regarded as highly electronegative.
Due to the uneven electron sharing among the atoms, insignificantly (δ+) positive or (δ-) negative charges are originated.
This charge is known as a partial charge, also termed as a dipole that is an essential characteristic of the water molecule and is also considered for several of the features of water.
You can also read out the article on the polarity of H2O.
2. Non-polar Covalent Bond
When the difference in the electronegativity among the participating atoms is zero, it leads to the formation of a non-polar covalent bond.
In this type of bond, the sharing of electrons is equal among the atoms.
Check out the article on the polarity of Cl2.
3. Coordinate or Dative Covalent Bond
A coordinate or dative covalent bond is formed when the shared electron pairs are gained from one of the participating atoms.
This class of bonding is usually seen in the bonding of metal ions with ligands.
Features of Covalent Bond
1. Covalent bonds are accountable for the overall function of stable covalent compounds. The properties of a covalent bond are listed below.
2. The sharing of electrons among the participating atoms forms a covalent bond.
3. The covalent bonds connecting different atoms can be classified as single, double, or triple bonds.
4. Covalent bonds are formed among two nonmetals or formed among a nonmetal and a metalloid.
5. Covalent bonds are strong and stable, and high energy is needed for bond breaking to carry out the reaction
6. The melting point and boiling points of covalent compounds are very low.
7. The conduction of electricity is not possible in the covalent bond.
8. They are not soluble in water, which is a polar solvent. Still, they are soluble in benzene, which is a non-polar solvent.
9. Covalently bonded compounds are stable and react almost slowly.
What is an Ionic Bond?
The electrostatic attraction binds the two oppositely charged ions collectively and is termed the ionic bond.
The chemical bond is formed among two participating atoms by the total shift of one or more electrons from one atom to the other, thereby achieving their inert gas configuration.
There are essentially three methods for two atoms to link to spend energy and acquire stability. One approach is gaining or losing electrons to achieve octet configuration. The bond produced by this type of method is called an ionic bond.
This class of bond is made when one atom takes electrons, whereas the other atom gives electrons from its valence orbital.
Ionic Bond Characteristics
The ionic bonded molecules possess a strong force of attraction among cations and anions, and the following characteristics are seen:
1. The ionic bonds are the strongest of all the bonds.
2. The charge is separated in ionic bonded molecules, and thereby they are the most reactive of all the bonds in the given condition.
3. The molecules having ionic bonds have high melting and boiling point.
4. When dissolved in water or in the molten state, the ionic bonded molecules conduct electricity. This is because of the ions, which serve as charge carriers.
The type of a bond among two participating atoms can be estimated by calculating the electronegative value among the atoms involved in bonding.
The range of electronegativity values for the type of bonds is listed below.
|Bond Type||Electronegativity value|
|Polar Covalent Bond||0.5 to 1.9|
|Non-polar Covalent Bond||0 to 0.4|
|Ionic Bond||2.4 to 4.0|
Since we know the concept of covalent and ionic bonding, let us now move on to understand the reason behind the covalent bonding in hydrogen fluoride.
Why HF is a Covalent Compound?
Hydrogen fluoride is a polar covalent bond. The intermediate of an ionic and a covalent bond is considered a polar covalent bond. The polar covalent bond is depicted by an arrow.
Electronegativity is described as the capacity of an atom to pull electrons towards itself. In a hydrogen fluoride molecule, the electronegativity of hydrogen is 2.2, the electronegativity of fluorine is 3.98. Thus, the electronegativity difference is 1.78.
HF is a polar covalent compound. Fluorine is the highly electronegative atom amongst all the halogens. It reacts with hydrogen forming a covalent compound.
However, hydrogen fluoride is polar as fluorine changes the electron cloud density of hydrogen by attracting electrons to itself.
Hence, the electron cloud density is attracted by fluorine, forming a polarized compound because of the significant electronegative difference.
Therefore, due to the transfer of electrons, hydrogen acquires a partial positive charge, and fluorine carries a partial negative charge.
Even if hydrogen fluoride forms a covalent bond, due to the electronegativity difference, the electron density is unequally distributed, developing a partial ionic character.
Preparation of Hydrogen Fluoride
Typically, the reaction of fluorine with hydrogen forms the gaseous hydrogen fluoride.
CaF2 is reacted with concentrated. sulphuric acid to form aq. hydrogen fluoride.
CaF2 + concentrated H2SO4 —–> CaSO4 + 2HF
While anhydrous hydrogen fluoride is formed by heating KHF2 at 573 K in a copper counter.
KHF2 —-> KF + HF
Properties of Hydrogen Fluoride
1. HF is a colorless gas or liquid having a 20.06 g/mol molar mass. The density of HF is 1.15 g/L. HF exhibits a melting point of -83.6 ℃ and a B.P of 19.5 ℃.
2. HF when combined with water or absorb moisture leads to the formation of hydrochloric acid.
Thus, it is considered hazardous when HF accidentally touches skin or body parts, as it destroys the tissue because of its corrosive nature.
3. HF possesses an unusual feature of elevated M.P and B.P when matched with other hydrogen halides due to the intermolecular hydrogen bonding.
Application of Hydrogen Fluoride
1. Hydrogen fluoride is employed to prepare various pharmaceutical products and various polymers.
The polytetrafluoroethylene, which is commonly known as Teflon, is prepared using hydrogen fluoride.
2. Approximately 60%-70% of HF is employed in the production of various ingredients of refrigerants that are broadly valuable globally in the use of freezers and air conditioners.
3. It is utilized for cleansing and purification of several automotive gears, tools, and others due to its high corrosive action.
It can be concluded that HF is a polar covalent compound. Fluorine being a highly electronegative atom reacts with hydrogen forming a covalent compound. But HF is polar because of the difference in electronegativity. The electron density is unequally distributed, developing a partial ionic character.
Hence, hydrogen fluoride forms a covalent bond, and due to the difference in electronegativity, the bond develops a partial ionic character.