A bond is a collection of two electrons from different atoms (mostly), forming a pair and fulfilling the basic purpose of bonding i.e. completing octets of atoms. Atoms need to complete octets in order to be stable i.e. lower their energy.

Octet completion is a condition where an atom has eight electrons in the outermost electronic shell. The reason is that ‘eight’ is the most stable configuration for electrons after two (for duplet completion). It keeps maximum distance between repelling electronic pairs.

An ionic bond is an electrostatic force of attraction between two oppositely charged (may be partially charged) atoms/ions. This electrostatic force becomes the reason to hold the constituent atoms of an ionic bond, together.

Formation of ionic bond

Ionic bonds are formed when there is a large electronegativity difference between integrating atoms. As a convention, one of the bonded atoms is supposed to be a cation, and the other one, an anion. The purpose of this assumption is to show that the electron(s) are getting transferred from one of the atoms to the other.

Ionic bonding in Lithium fluoride (LiF)

Lithium fluoride is an ionic compound having an electronegativity difference of (4.0 – 0.98) = (3.02). The duplet of lithium needs to be completed for its stability by the loss of one electron, whereas fluorine needs an electron to complete its octet, which they accomplish by forming an ionic bond between them.


Ionic bond in potassium chloride (KCl)

Potassium chloride (KCl) an ionic compound (3.16 – 0.82) = (2.34). Potassium sort of loses its electron, which chlorine gains to form an ionic bond.

These pictures do not show a complete transfer of electrons from donor to acceptor atoms because;

The general rule of electrons leaving an atom and getting added to one, for making cations and anions is quite mistaken. Actually, electrons never leave or get added to an atom entirely. This does happen, but only to a limited extent, which could be called, “the atomic vicinity of an atom being extended or reduced”. It means that electron(s) get farther from one nucleus and near to the other one but they still exist in their individual atomic vicinities. In short, electrons never entirely leave or add to atoms when making bonds. They just extend their distance from one nucleus and reduce it from another.

It means that an ionic bond is actually a covalent bond, except that it is excessively more polar than even polar covalent ones.

Electronegativity difference

The term electronegativity is explained as the difference in the abilities of atoms to attract the bonded (shared pair) of electrons. The higher the electronegativity an atom has, the higher chances it gets to have bonded electrons nearer and lower the electronegativity, the higher the electropositivity i.e. the atom likes to keep electrons at a distance.

Electronegativity difference is the parameter that decides whether a bond is ionic or covalent. It also tells whether the bond is polar covalent or non-polar.

Type of bond Polarity Electronegativity difference (ΔEN)
Ionic bond Polar above 1.7
Covalent bond Polar 0.4 to 1.7
Nonpolar 0 to 0.40

Properties imparted by ionic bonds

The electrostatic force of attraction between cationic and anionic spheres is such a great force, which makes ionic substances crystals. These crystals are considerably hard and non-volatile. Ionic characters of constituent atoms make these compounds conductors in aqueous and molten states but due to the lattice arrangement and fixed attractions of electrons, solid states of these compounds are non-conductors.

Ionic solids are very brittle, which becomes the reason for their crystalline existence.

Related Topics

Key Takeaways

  • An ionic bond is actually a covalent bond with an extremely high electronegativity difference (polarity).
  • The ionic bond is the strongest among intramolecular forces (bonds).
  • Ionic bonds are the most polar bonds and create dipoles.
  • The electrostatic forces of attraction between volunteer positive and negative charges make a bond strong enough to call it an ionic bond.
  • Ionic solids exist as brittle, and crystals are strong but soluble in water.
  • Ionic substances are non-conductors in solid states, but they conduct in molten states.
  • It is the electronegativity difference that decides whether a compound will have an ionic bond, a polar covalent bond, or a non-polar covalent bond.

Electronegativity values for type of bonds - ionic -covalent (polar and non polar)

Concepts Berg

How do ionic bonds form?

Ionic bonds are formed by the electrostatic force of attraction between two oppositely charged (opposite-natured) atoms. It is in fact a covalent bond, with an extremely high electronegativity difference between the atoms. For an ionic bond to form, the electronegativity difference among those atoms must be greater than (1.7).

Why do Ionic bonds form?

Ionic bonds form because atoms need electrons to keep their octet complete either by getting lost or being added into the atoms. They form to complete the octet number of electrons in atoms by taking electrons from one atom and inserting them into the other in order to make stable compounds (ionic compounds).

Is NaCl ionic or covalent?

NaCl is a pure ionic compound. For a compound to be ionic in nature, the electronegativity difference among constituent atoms must be greater than 1.7 which is 2.23 in the case of table salt, the NaCl.

Are ionic bonds strong?

Ionic bonds are the strongest intramolecular forces, a compound can have. The highest electronegativity difference among atoms (ΔEN > 1.7) corresponds to an ionic bond in the compound. Compounds having ionic bonds are called ionic compounds. Moreover, ionic bonds are the electrostatic forces among compounds while other types of intramolecular bonds are just the mutual sharing of electrons, making ionic bonds, the strongest.

What are 20 examples of ionic bond compounds?

The bonds among electropositive and electronegative atoms of these compounds are ionic bonds.

  • Copper(I) fluoride (CuF)
  • Copper(II) sulphide (CuS)
  • Cobalt(II) oxide (CoO)
  • Lead(II) sulphide (PbS)
  • Nickel(II) oxide (NiO)
  • Lithium fluoride (LiF)
  • Lithium bromide (LiBr)
  • Lithium chloride (LiCl)
  • Iron(II) sulphide (FeS)
  • Iron(II) oxide (FeO)
  • Sodium chloride (NaCl)
  • Sodium sulphite (Na2SO3)
  • Sodium hydrogen phosphate (NaHPO4)
  • Magnesium sulphate (MgSO4)
  • Potassium phosphate (K3PO4)
  • Potassium iodide (KI)
  • Sodium hydroxide (NaOH)
  • Sodium carbonate (Na2CO3)
  • Sodium bicarbonate (NaHCO3)
  • Sodium fluoride (NaF)

Is a hydrogen bond a covalent bond or ionic?

A hydrogen bond is polar covalent in nature because of the large electronegativity difference between atoms (O, N, and Cl) and (H) but not large enough to make it an ionic bond. Hydrogen has an average value of electronegativity value (2.20), which makes it impossible for any atom to have a higher electronegativity difference than (1.7), required to make a bond ionic in nature.

Who discovered ionic bonding?

Gilbert Newton Lewis discovered ionic bonding in 1916, although he named it ‘chemical bonding’ and said that, A chemical bond is a pair of electrons shared by two atoms“.

Why do ionic bonds form?

Ionic bonds form because of the electrostatic forces of attraction present between a positively charged ‘cation’ and a negatively ‘charged’ anion. The atoms of an ionic compound are either so electronegative or electropositive, that their tendency to donate or accept electrons is seen as apparent charges. These apparent charges are balanced by the formation of an ionic bond.

What is the importance of ionic bonds?

Ionic bonds or in fact ionic compounds are important because of their lattice structures, their high solubility in water, the conducting (molten or aqueous), and nonconducting (solid or lattice) states. The importance of ionic bonds is frequently seen in inorganic chemistry, because of highly electronegative and electropositive atoms, rather than organic chemistry because of the low electronegativity difference between atoms i.e. C (2.5) and H (2.20).

Which is the strongest ionic bond in the world?

The strongest ionic bond exists in cesium fluoride because of the very high electronegativity difference (4.0 – 0.8) = 3.20. However, theoretically, a stronger ionic bond may exist that is francium fluoride (4.0 – 0.7) = 3.30, but due to the extreme rarity of francium, CsF (cesium fluoride) is considered the strongest ionic bond.

Is hydroxide an ionic bond compound?

Hydroxide (OH) is not an ionic bonded radical. The electronegativity difference i.e. ((O) 3.44 – (H) 2.20) = 1.24, does not lead to ionic bond formation. However, hydroxide ion (OH) is counted as an ‘ion’ because of an extra electron on the oxygen atom.

What is meant by ionic character?

Ionic character is the property of a compound to exhibit ionic bond formation capability. The ionic character of an atom increases, as its electronegativity increases or electropositivity decreases. Two differently charged atoms with large ionic characters when combined, make ionic compounds.

What are four facts about the ionic bond compounds?

  1. Ionic compounds are three dimensionally fully arranged, making lattice structures.
  2. Ionic bonds are always formed by the combination of metals and non-metals.
  3. These compounds are conductors in molten states and non-conductors in solid.
  4. Ionic compounds are relatively more stable than covalent ones.

Which 2 types of elements are involved in ionic bonds?

The types of elements involved in ionic bonding are apparent cations (positively charged) and anions (negatively charged).

Why can’t hydrogen atoms form an ionic bond?

Hydrogen atoms have an electronegativity value of 2.20, which is almost the average of overall (0 to 4.0) values. This property makes it impossible to find an atom having enough electronegativity, to make a difference of more than 1.7 (a requirement for ionic character) on the electronegativity difference scale.

Are acids ionic or covalent?

Protic acids are generally polar covalent in nature. This is due to the fact that hydrogen cannot form ionic bonds. On the other hand, acids having no hydrogen (Lewis acids), can have ionic bonds.

Is sodium nitride an ionic or a covalent bond?

Sodium nitride (Na3N) is a good ionic compound. The fact that sodium nitride behaves like semiconductors while conduction is because of its lattice arrangement i.e. Anti ReO3.

Why is an ionic bond not double or triple like a covalent bond?

Covalent bonds are the mutual sharing of electrons based on numbers i.e. two electrons make a bond, four will make a double bond, and so on. But in the case of the ionic bonds, it is the electrostatic attraction between cations and anions, shown by a line as a convention. The reason for this attraction is their electronegativity difference, not the number of electrons. That is why an ionic bond cannot be called double, or triple like covalent bonds.