Covalent Bonds vs. Ionic Bonds

Covalent Bonds
Ionic Bonds

There are two types of atomic bonds - ionic bonds and covalent bonds. They differ in their structure and properties. Covalent bonds consist of pairs of electrons shared by two atoms, and bind the atoms in a fixed orientation. Relatively high energies are required to break them (50 - 200 kcal/mol). Whether two atoms can form a covalent bond depends upon their electronegativity i.e. the power of an atom in a molecule to attract electrons to itself. If two atoms differ considerably in their electronegativity - as sodium and chloride do - then one of the atoms will lose its electron to the other atom. This results in a positively charged ion (cation) and negatively charged ion (anion). The bond between these two ions is called an ionic bond.

Comparison chart

Covalent Bonds

Ionic Bonds

Polarity Low High
Formation A covalent bond is formed between two non-metals that have similar electronegativities. Neither atom is "strong" enough to attract electrons from the other. For stabilization, they share their electrons from outer molecular orbit with others. An ionic bond is formed between a metal and a non-metal. Non-metals(-ve ion) are "stronger" than the metal(+ve ion) and can get electrons very easily from the metal. These two opposite ions attract each other and form the ionic bond.
Shape Definite shape No definite shape
What is it? Covalent bonding is a form of chemical bonding between two non metallic atoms which is characterized by the sharing of pairs of electrons between atoms and other covalent bonds. Ionic bond, also known as electrovalent bond is a type of bond formed from the electrostatic attraction between oppositely charged ions in a chemical compound. These kinds of bonds occur mainly between a metallic and a non metallic atom.
Melting point low High
Examples Methane (CH4), Hydro Chloric acid (HCl) Sodium chloride (NaCl), Sulphuric Acid (H2SO4 )
Occurs between Two non-metals One metal and one non-metal
Boiling point Low High
State at room temperature Liquid or gaseous Solid

Contents: Covalent Bonds vs Ionic Bonds

About Covalent and Ionic Bonds

The covalent bond is formed when two atoms are able to share electrons whereas the ionic bond is formed when the "sharing" is so unequal that an electron from atom A is completely lost to atom B, resulting in a pair of ions.

Each atom consists of protons, neutrons and electrons. At the centre of the atom, neutrons and protons stay together. But electrons revolve in orbit around the centre. Each of these molecular orbits can have a certain number of electrons to form a stable atom. But apart from Inert gas, this configuration is not present with most of the atoms. So to stabilize the atom, each atom shares half of its electrons.

Covalent bonding is a form of chemical bonding between two non metallic atoms which is characterized by the sharing of pairs of electrons between atoms and other covalent bonds. Ionic bond, also known as electrovalent bond is a type of bond formed from the electrostatic attraction between oppositely charged ions in a chemical compound. This kind of bonds occurs mainly between a metallic and a non metallic atom.

Formation and examples

Covalent bonds are formed as a result of the sharing of one or more pairs of bonding electrons. The electro negativities (electron attracting ability) of the two bonded atoms are either equal or the difference is no greater than 1.7. As long as the electro-negativity difference is no greater than 1.7, the atoms can only share the bonding electrons.

A model of the double and single covalent bonds of carbon within a benzene ring.
A model of the double and single covalent bonds of carbon within a benzene ring.

For example, let us consider a Methane molecule i.e.CH4. Carbon has 6 electrons and its electronic configuration is 1s22s22p2, i.e. it has 4 electrons in its outer orbit. According to the Octate rule ( It states that atoms tend to gain, lose, or share electrons so that each atom has full outermost energy level which is typically 8 electrons.), to be in a stable state, it needs 4 more electrons. So it forms covalent bond with Hydrogen (1s1), and by sharing electrons with hydrogen it forms Methane or CH4.

If the electro-negativity difference is greater than 1.7 then the higher electronegative atom has an electron attracting ability which is large enough to force the transfer of electrons from the lesser electronegative atom. This causes the formation of ionic bonds.

Sodium and chlorine bonding ionically to form sodium chloride.
Sodium and chlorine bonding ionically to form sodium chloride.

For example, in common table salt (NaCl) the individual atoms are sodium and chlorine. Chlorine has seven valence electrons in its outer orbit but to be in a stable condition, it needs eight electrons in outer orbit. On the other hand, Sodium has one valence electron and it also needs eight electrons. Since chlorine has a high electro-negativity, 3.16 compared to sodium’s 0.9, (so the difference between their electro-negativity is more than 1.7) chlorine can easily attract sodium's one valence electron. In this manner they form an Ionic bond, and share each other’s electrons and both will have 8 electrons in their outer shell.

Examples (video)

Characteristics of the bonds

Covalent bonds have a definite and predictable shape and have low melting and boiling points. They can be easily broken into its primary structure as the atoms are close by to share the electrons. These are mostly gaseous and even a slight negative or positive charge at opposite ends of a covalent bond gives them molecular polarity.

Ionic bonds normally form crystalline atoms and have higher melting points and boiling points compared to covalent compounds. These conduct electricity in molten or solution state and they are extremely polar bonds. Most of them are soluble in water but insoluble in non-polar solvents. They require much more energy than covalent bond to break the bond between them.

The reason for the difference in the melting and boiling points for ionic and covalent bonds can be illustrated through an example of NaCl (ionic bond) and Cl2 (covalent bond). This example can be found at Cartage.org.

Video comparing types of atomic bonds

Further Reading

Some good books on Covalent and Ionic bonds are available on Amazon.com:

References

Share this comparison:

If you read this far, you should follow us on:

"Covalent Bonds vs Ionic Bonds." Diffen.com. Diffen LLC, n.d. Web. 21 Aug 2014. < http://www.diffen.com/difference/Covalent_Bonds_vs_Ionic_Bonds >

Stay informed Related Comparisons
Follow Diffen
Make Diffen Smarter.

Log in to edit comparisons or create new comparisons in your area of expertise!

Sign up »
Top 5 Comparisons Recently Compared

Comments: Covalent Bonds vs Ionic Bonds

Comments via Facebook

Anonymous comments (15)

June 17, 2014, 9:46am

well this is so interesting and east y to understand, I really enjoyed.

— 41.✗.✗.131
0

January 19, 2014, 3:12pm

the bond formation between IIA group element & halides is covalent or ionic.......

— 37.✗.✗.245
0

May 17, 2014, 6:33pm

Thank-you, this was super clear and helpful :)

— 68.✗.✗.50
-1

March 16, 2014, 5:29am

How can covalent bonds have a definite shape if it is in a liquid or gas state?
Think you need to check on that ...

— 202.✗.✗.225
-1

September 21, 2013, 2:31am

Thank you!! Very helpful!

— 142.✗.✗.26
-1

March 6, 2013, 8:10pm

I think this is a really good site. Helped me a lot. However, it should really expand on the differences and similarities between the two types of bonding. Overall, I understand these types of bonding so much more now. Also, it is really easy to remember thanks to the simple lay out.

— 86.✗.✗.171
-1

December 12, 2012, 2:11pm

thanks for this website. Helped me on my science pack it. (:

— 208.✗.✗.254
-1

December 9, 2012, 6:53am

which bond is strong?

— 182.✗.✗.34
-1

December 4, 2012, 8:39pm

yes me too.

— 216.✗.✗.178
-1

December 4, 2012, 9:51am

i have found this website so useful and benificial for me and.i am happy today due to getting more information about ionic as well as covalent bond. thanks for that

— 119.✗.✗.221
-1

March 14, 2012, 3:16am

For the boiling point thing it's easy to remember HIGH "I" for ionic because it has a high boiling point. And for covalent it can be CO LOW because covalent has a low boiling point. Hope it helps

— 184.✗.✗.186
-1

February 12, 2012, 6:57pm

Awesome! I've been really having difficulty understanding it but I finally understood by reading this. thanks

— 188.✗.✗.37
-1

December 25, 2011, 1:31pm

very nice different is given in tabulated form, but I think their should be strength different also to be given.

— 117.✗.✗.69
-1

December 8, 2011, 1:18am

Very Well written, I will definately be coming back for more!!

— 173.✗.✗.113
-1

December 6, 2011, 5:58am

some of this is false...like how covalent ONLY happens between 2 non metals. Thats totally untrue. You need to replace it with "in most cases"

— 76.✗.✗.84
-1

share

Up next

Anion vs. Cation