Is HF (Hydrogen Fluoride) Covalent or Ionic?

A hydrogen atom and a fluorine atom make up hydrogen fluoride, which has the chemical formula HF. Hydrogen fluoride has a molecular weight of 20.01 g/mol.

Hydrogen fluoride is a colourless gas or liquid with an unpleasant odour. Hydrofluoric acid is the aqueous version of hydrogen fluoride.

It’s a crucial ingredient in the production of medications and polymers, among other things.

Hydrogen fluoride is a dangerous gas that reacts with moisture to generate caustic hydrofluoric acid.

The gas can also cause blindness due to the rapid breakdown of the corneas, which is why it is stored in cylinders.

In this article, we’ll look at whether HF is a covalent or ionic molecule.

Is HF ionic or covalent, then? Because the more electronegative fluorine atom and the less electronegative hydrogen atom share electrons unequally, hydrogen fluoride is a covalently linked polar molecule. Because fluorine is bound to non-metallic hydrogen, the electronegativity difference between hydrogen and fluoride is 1.78, and it is considered polar covalent.

Let’s look at the difference between covalent and ionic bonding.

What is the definition of a covalent bond?

A covalent bond is formed when two or more atoms share electron pairs.

The electrical force of attraction between their nuclei and the electrons causes them to connect. It has the ability to hold all of the atoms together.

Using the octet rule, the atoms share electrons to establish a stable electrical state.

Covalent compounds are defined as compounds with covalent bonding. Covalent bonds, also known as molecular bonds, are the most frequent type of bond in organic chemistry, as opposed to ionic bonds.

The covalent bond is a type of bond that is formed

If the electronegativity gap between the involved atoms is significantly less, a covalent bond is formed.

The ability of an atom to attract electrons to itself is known as electronegativity. The atoms form covalent bonds with each other to provide greater stability, which is achieved by sharing valence electrons and forming a full valence shell.

The electrostatic attraction between positively charged nuclei binds the distinct atoms collectively, and the negatively charged electrons are more significant than the repulsion between identically charged nuclei.

As a result, the molecules are stabilised as a result of this attraction.

The force required to break a covalent bond, which is the total energy required to divide the covalently bound atoms, determines the bond’s intensity.

Covalent Bonds of Various Types

The number of shared electron pairs, the bond polarity, and the atoms’ coordination are used to arrange a covalent connection.

Covalent bonds are divided into three categories based on the electron pairs that are shared.

Covalent Bond (Single)

A single covalent link, also known as a single bond, is formed when a pair of electrons or a total of two electrons are shared among the atoms.

H2 is an example.

Covalent link with two atoms

A double covalent bond, also known as a simple double bond, is formed when two electron pairs or a total of four electrons are shared among the atoms.

CO2 is an example.

Covalent Bond (Triple)

A triple covalent bond, also known as a simple triple bond, is formed when three electron pairs or a total of six electrons are shared among the atoms.

N2 is an example.

Covalent bonds are categorised into three groups based on the polarity of the bond and the coordination of the atoms:

Covalent Polar Bond

If the electronegativities of the sharing atoms differ significantly, a polar covalent bond is formed.

The electronegativity gap between polar covalent bonds is in the range of 0.1 to 2.

As a result, the bound electron pair is drawn toward the higher electronegative atom, turning it slightly negative while the opposite atom turns slightly positive.

The sharing of electrons between the atoms is unequal when the relationship is a polar covalent bond, because they are strongly drawn to one nucleus over the other.

Furthermore, an atom is considered strongly electronegative if it pushes electrons in its direction with a greater force.

Insignificantly (+) positive or (-) negative charges are generated as a result of unequal electron sharing among the atoms.

This charge is known as a partial charge, also known as a dipole, and it is an important attribute of the water molecule, as well as a factor in several of its properties.

H2O is a good example.

You can also read about the polarity of H2O in this article.

Covalent Bond That Isn’t Polar

The creation of a non-polar covalent bond occurs when the difference in electronegativity among the involved atoms is zero.

The atoms in this sort of relationship share the same number of electrons.

Cl2 is a good example.

Take a look at the article on Cl2 polarity.

Dative or Coordinate Covalent Bond

When one of the involved atoms gains the shared electron pairs, a coordinate or dative covalent bond is created.

The bonding of metal ions with ligands is an example of this type of bonding.

CO is a good example.

Covalent Bond Characteristics

  1. The overall function of stable covalent compounds is determined by covalent bonds. A covalent bond’s qualities are listed below.
  2. A covalent bond is formed when the participating atoms share electrons.
  3. There are three types of covalent connections that connect various atoms: single, double, and triple bonds.
  4. Covalent bonds are produced when two nonmetals or a nonmetal and a metalloid come together.
  5. Covalent bonds are strong and stable, and bond breaking requires a lot of energy to complete the reaction.
  6. Covalent compounds have extremely low melting and boiling points.
  7. Electricity cannot be conducted through the covalent bond.
  8. They are not soluble in polar solvents such as water. They are, nevertheless, soluble in benzene, a non-polar solvent.
  9. Compounds that are covalently linked are stable and react slowly.

What is the definition of an ionic bond?

The ionic bond is formed when electrostatic attraction joins two oppositely charged ions together.

The entire shift of one or more electrons from one atom to the other forms the chemical bond between two participating atoms, resulting in their inert gas condition.

There are basically three ways for two atoms to connect in order to spend energy and gain stability. To obtain octet configuration, one method is to add or lose electrons. An ionic bond is the sort of bond created by this approach.

When one atom gets electrons from its valence orbital, the other atom gives electrons from its valence orbital.

Characteristics of Ionic Bonds

Ionic linked molecules have a high attraction between cations and anions, resulting in the following characteristics:

  1. Ionic bonds are the most powerful of all binds.
  2. Ionic bonded molecules have their charge separated, making them the most reactive of all the bonds in the given circumstances.
  3. Ionic bond molecules have a high melting and boiling point.
  4. Ionic linked molecules conduct electricity when dissolved in water or in a molten state. Because of the ions, which act as charge carriers, this is the case.

Calculating the electronegative value of the atoms involved in bonding can be used to estimate the type of bond between two participating atoms.

The following table shows the range of electronegativity values for each bond type.

Electronegativity of Bond Type

0.5 to 1.9 Polar Covalent Bond

0 to 0.4 Non-polar Covalent Bond

2.4 to 4.0 Ionic Bond

Now that we’ve covered the basics of covalent and ionic bonding, let’s look at why covalent bonding occurs in hydrogen fluoride.

Why is HF classified as a covalent compound?

The covalent connection between hydrogen and fluoride is polar. A polar covalent bond is an intermediary between an ionic and a covalent link. An arrow represents the polar covalent bond.

The ability of an atom to attract electrons to itself is known as electronegativity. The electronegativity of hydrogen is 2.2, and the electronegativity of fluorine is 3.98 in a hydrogen fluoride molecule. As a result, the difference in electronegativity is 1.78.

HF is a polar covalent molecule with a positive charge. Among all the halogens, fluorine is the most electronegative. It forms a covalent molecule when it interacts with hydrogen.

Hydrogen fluoride, on the other hand, is polar because fluorine affects the density of hydrogen’s electron cloud by drawing electrons to itself.

As a result of the substantial electronegative difference, fluorine attracts the electron cloud density, generating a polarised molecule.

As a result of the electron transfer, hydrogen gains a partial positive charge, while fluorine gains a partial negative charge.

Even if hydrogen fluoride forms a covalent link, the electron density is unequally distributed due to the electronegativity difference, giving it a partial ionic nature.

Hydrogen Fluoride Preparation

Fluorine reacts with hydrogen to produce hydrogen fluoride, which is a gas.

The reaction of CaF2 with concentrated sulphuric acid produces aqueous hydrogen fluoride.

CaF2   +   concentrated H2SO4   —–>     CaSO4   +   2HF

KHF2 is heated to 573 K in a copper counter to produce anhydrous hydrogen fluoride.

KHF2   —->  KF  +  HF

Hydrogen Fluoride’s Characteristics

  1. HF is a colourless gas or liquid with a molar mass of 20.06 g/mol. HF has a density of 1.15 g/L. HF has a melting point of -83.6 °C and a boiling point of 19.5 °C.
  2. Hydrochloric acid is formed when HF is mixed with water or absorbs moisture.

As a result, when HF comes into contact with skin or other body components, it kills the tissue due to its corrosive nature.

  1. Due to intermolecular hydrogen bonding, HF has an uncommon property of having higher M.P and B.P when compared to other hydrogen halides.

Hydrogen fluoride is used in the production of a variety of pharmaceuticals and polymers.

Teflon is made from polytetrafluoroethylene (PTFE), which is made from hydrogen fluoride.

  1. About 60-70 percent of HF is used in the synthesis of various refrigerant chemicals that are widely used in the use of freezers and air conditioners around the world.
  2. Due to its significant corrosive activity, it is used to clean and purify a variety of automotive gears, tools, and other items.


HF is a polar covalent molecule, as can be deduced. Fluorine is a strongly electronegative atom that forms a covalent combination with hydrogen. However, due of the difference in electronegativity, HF is polar. The electron density is unevenly distributed, giving the material a somewhat ionic appearance.

As a result, hydrogen fluoride forms a covalent bond, which takes on a partial ionic character due to the difference in electronegativity.

Read more: Is H2S an ionic or a covalent compound?

Misha Khatri
Misha Khatri is an emeritus professor in the University of Notre Dame's Department of Chemistry and Biochemistry. He graduated from Northern Illinois University with a BSc in Chemistry and Mathematics and a PhD in Physical Analytical Chemistry from the University of Utah.


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