The three main types of chemical bonds are ionic bonds, covalent bonds, and metallic bonds. The type of bond determines the structure, stability, and properties of a substance.
Chemical bonds can affect the stability of a compound; those with weak chemical bonds are usually less stable. Bonds also dictate the type of reactions that a substance can undergo, as well as the amount of energy involved.
Bonds are central to the study and practice of chemistry. From simple inorganic molecules to complex biochemical compounds, chemical bonds play crucial roles in the behaviours of substances. Metallic bonds, for instance, are produced by delocalised electrons that are spread out through the molecular lattice structure of the metal. This is why metals are very good conductors of electricity.
Understanding the types of chemical bonds is crucial for synthesising chemicals such as dyes, medicines, and biological molecules like hormones. It’s possible to manufacture complex chemicals from simpler chemicals when you know how these smaller molecules react together.
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Ionic Bonds
Ionic bonds, also known as electrovalent bonds, are a type of bond wherein the electrons are transferred from one atom to another atom. That means that one atom becomes positively charged as it loses electrons, while the other atom becomes negatively charged as it gains electrons.
Ionic compounds are most commonly formed between a metal and a non-metal. They typically take the form of a crystalline solid or salt.
Alkali metals like sodium and alkaline earth metals, such as magnesium, have strong affinities with non-metals, particularly fluorine and chlorine.
With the exception of astatine, the four halogens are very strong electrophiles. Below is a list of the five strongest electrophiles, along with the corresponding electrophilicity index.
- Fluorine: 3.86
- Chlorine: 3.67
- Bromine: 3.40
- Iodine: 3.09
- Hypochlorite: 2.52
The metals that form ionic bonds with electrophiles can also be ranked according to their reactivity. This means a more reactive metal can displace a less reactive metal in a substitution reaction.
For example, in the second group of elements in the periodic table, the alkaline earth metals are ranked as follows:
- Beryllium (Be)
- Magnesium (Mg)
- Calcium (Ca)
- Strontium (Sr)
- Barium (Ba)
- Radium (Ra)
The reactivity of these elements increases from top to bottom. Although they all readily donate their electrons to electrophiles, the reactivity increases as the atoms get bigger. As the size increases, the electrons move further from the nucleus. This lessens their attraction to the nucleus and they become increasingly easier to remove.
Definition and Formation of Ionic Bonds
An ionic bond is the strongest chemical bond between two atoms, common among salts and some minerals.
This type of bonds are crystal lattice structures with repeating patterns. Creating an ionic bond involves the transfer of the electron cloud from one element to another element, making one element positively-charged and the other negatively-charged.
Characteristics and Examples of Ionic Bonds
Substances with ionic bonds are generally solid under standard conditions. Typically, they are simple inorganic substances with two constituent elements or groups, one being metallic and the other non-metallic. They also have very high melting points.
These types of substances are neutral in pure form, but electrically conductive when dissolved in water. The most common substance that has ionic bonds is table salt. The ions of dissolved table salt play crucial roles in cellular functions, such as osmosis and chemical-electrical communications of muscles and neurons.
Another important example of a substance with ionic bonds is calcium carbonate. This is crucial in the structures and protection of many life forms, such as corals and crustaceans.
Applications of Ionic Bonds in Industry
One of the most common applications of ionic bonds in industry is in storing electrical power. Batteries, such as the lead batteries for car starters and lithium batteries for electronic gadgets, contain ionic compounds.
These compounds store and discharge electrical current in a controlled way. Ionic compounds are also used in electrolytic processes, such as for chrome plating automotive components. Ionic compounds, such as nitrates, are also commonly used as ingredients in the manufacture of a wide range of products, such as fertilisers.
What Is an Example of an Ionic Bond?
The most familiar example of an ionic bond is the bond between sodium and chlorine in sodium chloride, or table salt.
The ionic bond in sodium chloride is responsible for the crystalline solid structure of this substance. It’s also the reason why a solution of sodium chloride is good at conducting electricity. In fact, our body needs sodium chloride and trace amounts of other electrolytes to function properly.
Are Ionic Bonds Strong?
The ionic bonds in salts are strong due to the strong coulombic attractions between the ions. The opposite charges have strong attractions that require more energy to break compared to other types of bonds.
For example, it requires at least 769 kJ of energy to break the ionic bonds of one mole of sodium chloride. However, it takes only 436 kJ of energy to break the covalent bonds between the atoms of one mole of a diatomic hydrogen molecule.
Covalent Bonds
Many compounds, especially organic compounds and biological molecules, are covalently bonded. This type of bond is the norm between non-metal atoms.
Atoms that are covalently bonded share electrons almost equally. Compounds that have perfectly symmetrical sharing of electrons are non-polar, while those that have slightly asymmetric sharing of electrons are polar. Polar compounds, such as table sugar, can be dissolved in polar solvents like water. Conversely, non-polar compounds can only be dissolved in non-polar solvents, such as in the case of hydrocarbons.
Covalent bonds can either be single, double, or triple bonds. As bonds can be shared by more than two different atoms, molecules that are covalently bonded can form chains and rings. This makes covalent bonds ideal for large and complex organic molecules. 
Covalent bonds follow the octet rule, which means the outer shell must have eight electrons to become stable like the noble gases. As a result, molecules with covalently bonded atoms have regular or definite geometric shapes, such as tetrahedral, trigonal, and octahedral. The bond angles are also determined in this way. 
Understanding Covalent Bonds
Covalent bonds are a type of chemical bond that requires electron-sharing. This means that the outer electron clouds of the elements or groups of elements involved become mixed up, forming electron pairs.
However, unlike in ionic bonding, they are not completely captured by the other elements or groups of elements.
Properties of Covalent Bonds
Most compounds, organic and inorganic, have covalent bonds. They typically have low melting and boiling points, such as in the case of ice, which is a solid form of water. If the water is pure in ice form, it has a melting point of 0°C. Meanwhile, the boiling point of water is 100°C.
In comparison, table salt (ionic bond) has a melting point of 801°C and boiling point of 1,413°C. Compounds with covalent bonds are poor conductors of electricity and nonpolar compounds are typically insoluble in water.
Covalent Structures in Organic Chemistry
Covalent bonds are the dominant type of chemical bonds in organic chemistry compared to ionic bonds.
Many complex organic molecules, from linear to cyclic, from planar to spherical molecules like the Buckyball, all have covalent bonds. Polymers are also dominantly covalent. Covalent bonds allow molecules to form various structures because of the equal distribution of electrons between atoms.
What is an Example of a Covalent Bond?
The most common and important example of a covalent bond is water. Water contains single polar covalent bonds that make its molecules slightly bent at an angle of 104.5°.
The angle of the bonds between the oxygen atom and the two hydrogen atoms makes water a universal solvent that’s capable of dissolving virtually all polar compounds and ionic compounds.
Are Covalent Bonds Strong?
Although covalent bonds are generally weaker than ionic bonds, they provide stability and complexity to large organic molecules. Covalent bonds are common in many organic substances, such as starches. Large organic molecules require enzymes to be broken down.
Metallic Bonding
As the name suggests, metallic bonding is only present in elemental metals. It binds the metal atoms together into tightly-packed configurations. Consequently, the outermost electron shell of every atom overlaps with the shells of its neighbouring atoms. The electrons are delocalised, allowing them to move freely among the atoms. The non-localised electrons make the metal electrically conductive.
Nature of Metallic Bonding
The delocalised outermost electrons of elemental metals make metallic bonds behave in certain ways that give rise to metallic properties. For example, most metals have a shiny lustre.
Properties and Significance of Metallic Bonds
With a few exceptions, like mercury and gallium, metals are mostly solid under standard conditions. Many metallic bonds can exist in elemental forms, but some, such as sodium, are highly reactive to other elements.
Metallic bonds are typically malleable, excellent conductors of electricity, and can form alloys. These are all possible because the outermost electrons are non localised. These are special properties of metals that are not found in clusters in other substances.
Role of Metallic Bonds in Conductivity and Malleability
The loose electrons amongst the atoms of elemental metals allow the easy flow of electrical current. These electrons can easily be nudged to flow in one direction or the other. Depending on the source of power, they can either flow as direct current or as alternating current.
At the same time, the cloud of loose electrons makes metal easy to shape. A metal can be hammered or pressed to take certain shapes as the atoms slide with each other, and can retain its new shape as long as there is no external force or pressure.
What is an Example of a Metallic Bond?
All metal elements have metallic bonds. As well as electrical conductivity, the bonds can determine many of the other properties of metals.
Metallic bonds are responsible for making metals malleable, for instance, as the nuclei of the atoms can easily shift positions without breaking the bonds. Copper is one of the best examples of metals that exhibit malleability, electrical conductivity, and heat conductivity. 
Are Metallic Bonds Strong?
It may seem counterintuitive, but metallic bonds are actually weaker than both covalent and ionic bonds. This is because it takes less energy to break metallic bonds compared to covalent and ionic bonds.
Comparing Bond Types
The different types of chemical bonds have their own respective advantages and disadvantages. They can give rise to various chemical and physical properties that are unique to the specific types of elements involved. They have varying strengths and levels of stability.
Some examples of the differences between bond types include:
- Ionic bonds can form crystalline structures
- Covalent bonds can form polymers and biomolecules
- Metallic bonds can form alloys that have varying physical properties
- Ionic bonds can store electrical energy under certain conditions
- Covalent bonds can serve as electrical insulation
- Metallic bonds can induce electromagnetism and can exhibit superconductivity
Strength and Stability in Different Bonds
When ranked, ionic bond is the strongest chemical bond. The second strongest is covalent bond, meaning the weakest among the three is the metallic bond.
This is to do with the necessary energy needed to break the bonds between the bonded atoms. This means that substances with strong chemical bonds are also the most stable.
Practical Implications of Bond Types in Various Materials
Various types of bonds in various elements and compounds means that there are various ways that materials can be created.
Old materials can be improved and totally new materials can be created. There are trillions upon trillions of possible chemicals that can be created. One estimate puts it to 1×1060 possible compounds. Materials can have new properties that we only dreamed of, and this can lead to the creation of new medicines and nano-machines (molecular level), for example.
Conclusion
The three major types of chemical bond, namely, ionic, covalent, and metallic, largely determine the chemical and physical properties of substances. The potential compounds and materials that can be created are staggeringly many, and have seemingly unlimited applications in science and technology.
