What is an ionic bond?

Ionic bond - electrons are transferred

An ionic bond

An ionic bond is formed between elements of large differences in electronegativities, which are typically found between metals and non-metals.

The atom that loses the electron(s) becomes a positively charged ion called a cation, and the one that gains the electron(s) is called the anion.

Electronegativity bond scale

For ionic bonds, the electronegativity (EN) difference between two atoms is greater than 1.7

Electronegativity bond scale

The chart above shows the relationship between electronegativity difference and the bond type.

More about ionic bond scale

Electronegativity difference between Na and Cl

Let’s look at an example of an ionic bond formed between a sodium (Na) and chlorine (Cl) atom.

The electronegativity difference between sodium and chlorine is shown below:

Element Electronegativity
Sodium, Na 0.93
Chlorine. Cl 3.16
EN Difference = (3.16 – 0.93)

= 2.23

Since the difference is greater than 1.7, the bond between sodium and chlorine is considered an ionic bond.

Sodium chloride, NaCl

Sodium (Na) has 1 valence electron

Chlorine (Cl) has 7 valence electrons

Sodium and chlorine atoms

Chlorine is more electronegative than sodium

Sodium loses its valence electron to chlorine

Sodium transfers an electron to chlorine

An ionic bond is formed between sodium and chlorine

An electron is transferred in the formation of the ionic bond

Ionic bond forms between Na and Cl

Sodium, having lost 1 electron, becomes a positively charged ion called a cation

Chlorine, having gained 1 electron, becomes a negatively charged ion called an anion

Now, these oppositely charged ions attract each other

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