Lesson video

Hello, my name is Mr. Gundry, and I'm thrilled to be embarking on this learning journey with you today.

Together, we're going to explore some fascinating concepts in chemistry that will help us understand the world around us a little bit better.

Today's lesson is from our unit on the chemistry of carbon, entitled "Bonding to Carbon Atoms." By the end of this session, you'll be able to describe how carbon atoms can form up to four covalent bonds with other non-metal atoms. This is a fundamental concept that underpins our understanding of organic chemistry, building upon what we've previously learned about atomic structure and bonding.

I'm here to guide and support you through this learning process, and I'm confident we can master these concepts together.

Before we dive into the details, let's familiarise ourselves with some key terms that we'll be encountering today.

These include the octet rule, covalent bond, molecule, and organic compound.

These words will help us navigate through our lesson on carbon and its bonding capabilities.

Before we begin to dive too deep into the world of organic compounds, let's remind ourselves about covalent bonding and specifically look at the way that carbon covalently bonds to itself and other elements.

Compounds are substances formed when two or more different elements are chemically bonded.

This means that they're not just mixed together, but they're connected at the atomic level, creating a new substance with its own properties.

Interestingly, among all the elements, carbon forms more compounds than any other with the exception of hydrogen.

The reason behind this vast array of carbon compounds lies in carbon's unique atomic properties.

These properties allow carbon atoms to bond in diverse ways, leading to the immense variety of carbon-containing compounds that we see.

This versatility is a cornerstone of organic chemistry and is key to understanding the complexity of the molecules that are essential for life as we know it.

Chemical bonds occur because they enhance the stability of the substances.

This process involves elements either gaining, losing, or sharing electrons.

The ultimate goal for many of these elements is to fill their outermost shell with a total of eight electrons, which significantly contributes to their stability.

This principle is known as the octet rule.

It highlights an atom's tendency to adjust its electron configuration to achieve a valence shell, that's the outer shell, with eight electrons, mirroring the electron arrangement of a noble gas, which are inherently stable.

The octet rule is fundamental in understanding how atoms interact to form molecules and compounds, guiding the formation of chemical bonds in a way that seeks to achieve maximum stability through electron configuration.

Carbon, a non-metal found in group 4 of the periodic table, possesses four electrons in its outer shell.

To increase stability, carbon forms chemical bonds with other atoms, allowing it to achieve eight electrons in the outer shell.

The formation of these bonds allows carbon to adhere to the octet rule, which dictates that atoms are more stable when they have eight electrons in their valence shell, the outer shell.

This principle is a key factor in the chemical behaviour of carbon, enabling it to form a wide variety of compounds by sharing electrons with other atoms, thus achieving a full outer shell and increased stability.

Here we have a quick check on what we've covered so far.

Which two of the statements listed here about carbon are correct? Pause the video now to read through the answers, and press play when you're ready to move on.

Carbon atoms have six electrons in total, with four on the outer shell.

So this first answer is incorrect.

As we discussed, there are a large number of compounds containing carbon, with only hydrogen being more commonly found in compounds.

So this second statement is correct.

Carbon has four electrons on the outer shell of its atoms, as we've just discussed, so it is indeed found in group 4.

This means that the last statement must be incorrect, and we know this because carbon atoms will increase their stability by having a total of eight electrons on their outer shell.

Here's a true or false question for you, then.

The octet rule, so atoms are most stable with an outer shell containing eight electrons, only applies to carbon atoms. Is that true, or is that false? Well, it is in fact false.

So, over to you, which of these two reasons best explains why it's false? Pause now, and when you're ready to move on, hit the play button.

So, statement B suggests the carbon atoms need only four electrons in the outer shell to be stable.

However, carbon atoms do generally follow the octet rule, and so they will fill their electron shells, their outer shells, should I say, with a total of eight electrons.

Okay, carbon forms covalent bonds with other non-metal atoms through the sharing of electron pairs.

This sharing results in each atom contributing one electron to the bond, allowing both to approach the stable electron configuration as described by the octet rule.

The strength of covalent bonds comes from the electrostatic force of attraction, that's the positive and negative charge, attractive force, that's between the positively charged nuclei of the atoms involved and the shared negatively charged electrons.

These forces hold the atoms together tightly, creating a stable molecule.

The sharing of electrons in a covalent bond is fundamental, and it's one of the key aspects of chemistry that enables the formation of a wide variety of complex molecules essential for life and many synthetic materials.

With four electrons on its outer shell, carbon has the capacity to form up to four covalent bonds with other non-metal atoms, utilising its electrons to achieve a full outer shell of electrons.

This characteristic allows carbon to participate in the formation of a wide array of molecules by establishing varying types of covalent bonds.

The bonds carbon can form can be classified into three types based on the number of shared electron pairs.

Single bonds are where one pair of electrons is shared between carbon and another atom, resulting in the stable connection that fills one of the four available bonding sites around a carbon atom.

Double bonds involve two pairs of shared electrons, creating a stronger bond between carbon and another atom.

This fills two of carbon atoms' bonding sites.

And finally, triple bonds, where three pairs of electrons are shared, which is the strongest of these three types of bonding, and it engages three of each of the carbon atoms' available bonding sites.

This ability to form single, double, and triple bonds makes carbon extremely versatile in creating a diverse range of organic molecules, each with different properties and functions.

As we know, carbon atoms can combine with other non-metal atoms, and this creates a diverse range of molecules.

These molecules consist of two or more atoms held together by covalent bonds, which are formed through the sharing of electron pairs.

The capacity of carbon to engage in covalent bonding with various non-metals, including itself, underpins the complexity and variety of organic chemistry.

Through these bonds, carbon can construct an immense array of molecular structures, from simple molecules and compounds like carbon dioxide to complex polymers and biological macromolecules like proteins, each with unique properties and roles in nature and technology.

Dot-and-cross diagrams serve as a useful method for illustrating the covalent bonding in molecules containing carbon, such as carbon tetrachloride, CCl4.

These diagrams use dot and crosses to represent the valence, the outer shell electrons of different atoms, showcasing how electrons are shared to form covalent bonds.

For CCl4, the diagram centres on a carbon atom, which has four electrons in its outer shell.

Surrounding the carbon, each chlorine atom is depicted with seven valence electrons.

The diagram shows one electron from carbon and one from each chlorine atom coming together to form single covalent bonds.

Four of them.

This electron sharing enables the carbon atom to reach a stable arrangement with eight electrons in its outer shell.

And each chlorine atom also achieves a stable electron configuration by also completing its outer shell.

Through this visual representation, dot-and-cross diagrams highlight the distribution of electrons in molecules, demonstrating the formation of covalent bonds.

Okay, so which of these diagrams shows a molecule containing carbon atoms? Pause the video now to look at the diagrams and formulae, and when you're ready to move on, press play.

So, only option A, CO2, is a molecule containing carbon, as even though substance B has carbon in its formula, this is graphite.

This is a giant covalent substance.

Giant covalent substances are held together by covalent bonds, but they are not molecular in structure.

Substance C is dihydrogen sulphate, more commonly known as sulfuric acid when it's dissolved in water, and as we can see, it doesn't contain any carbon atoms. This question is a little different.

We've got three proposed molecules.

Which of these show molecules that could actually exist? Pause now to discuss your answers, and press play when you're ready to move on.

So the answers to this one are substance B and C, and this is because carbon has formed four covalent bonds, whereas in substance A, carbon has only formed two bonds.

This means carbon is not stable.

So carbon has formed a triple bond, so that's six shared electrons or three pairs with nitrogen in substance B, and it's formed one pair with hydrogen, giving the carbon atom a total of eight electrons on its outer shell.

We can see that in substance C that carbon has also formed four bonds, two to the oxygen in the form of a double bond and two to hydrogen.

That's one each to each of the hydrogen atoms. Here's a few statements to read through.

Which two statements below are correct about carbon atoms? Pause now to read through and select your answers, and when you're ready to continue, press play.

So we know that carbon atoms can form up to four covalent bonds with the aim of achieving a stable electron configuration of eight electrons on the outer shell.

They do this by sharing pairs of electrons with other non-metal atoms to form covalent bonds, and they can do this in single, double, or triple bonds.

Here's a set of questions for you to have a go at now to put all that we've just been through together into practise.

Your task includes writing the definition of a covalent bond, paying close attention to the electrostatic forces.

And the second part of the task is focused on drawing dot-and-cross diagrams for the four molecules shown.

Pause the video now to have a go at these questions, and when you're ready, press play for the answers.

So, a covalent bond is a type of chemical bond characterised by the sharing of a pair of electrons between atoms. This sharing allows the atoms to reach a more stable electron configuration.

The bond itself is maintained by the strong electrostatic forces of attraction between the positively charged nuclei of the atoms that are involved and the shared negatively charged electrons.

These forces keep the electrons closely associated with both nuclei, effectively holding the atoms together within the molecule.

Well done if you got each of those different parts to the definition of a covalent bond.

Dot-and-cross diagrams are used to illustrate how electrons are distributed in molecules, specifically showing how atoms share electrons in covalent bonding to fill their outer shells.

Often, aiming to fulfil the octet rule.

However, as you've probably realised, hydrogen is an exception to the octet rule, instead following the duet rule, aiming for two electrons in its outer shell due to the fact that it only has one shell of electrons that can only be filled to two electrons in total.

Let's discuss these given molecules.

So the first one is methane.

In methane, the carbon atom shares one of its four valence electrons, that's the outer shell electrons, remember, with each of the four hydrogen atoms. Since hydrogen atoms only need two electrons to fill their outer shell, and carbon needs eight, each shared pair of electrons allows all the atoms to achieve their respective stable configurations.

The carbon atom ends up with eight electrons on its outer shell, whilst each hydrogen has two.

In carbon dioxide, this features a carbon atom double bonded to two oxygen atoms. Each double bond consists of two shared pairs of electrons, totaling four electrons shared between a carbon and an oxygen.

This setup allows the carbon atom to have eight electrons in its valence shell, fulfilling the octet rule.

Oxygen, which also follows the octet rule, achieves this configuration by sharing electrons with carbon and through its own non-bonding lone pairs of electrons.

So you can see that it's got some just lone electrons on its outer shell, whereas carbon has all of its electrons in bonding.

For methanal, the carbon atom forms two single bonds with two hydrogen atoms and a double bond with an oxygen atom.

The single bonds with hydrogen each share a pair of electrons, and the double bond with oxygen shares two pairs.

This distribution ensures the carbon atom has eight electrons on its outer shell, whilst oxygen, through sharing and its own electrons, also fulfils the octet rule.

And again, hydrogen fulfilling the duet rule because it only has one electron to share, so it only gets one electron back.

And then finally, hydrogen cyanide has a triple bond between the carbon and nitrogen atoms and a single bond between the hydrogen and the carbon.

The triple bond involves three shared pairs of electrons between carbon and nitrogen, allowing both to fulfil that octet rule and have eight electrons on their outer shell.

The single bond with hydrogen contributes two electrons to carbon's outer shell and therefore also to hydrogen's.

So fulfilling the outer shell to be complete.

In summary, these diagrams illustrate the sharing of electrons to ensure that each atom achieves a stable electron configuration, with hydrogen as the notable exception aiming for two instead of eight electrons.

Well done if you got those right.

Remember, we should be aiming for pairs of electrons to exist in the shared space between each atom in a covalent bond.

We're now going to apply our understanding and knowledge of carbon's chemistry by looking at different types of compounds that contain carbon.

And we call these organic compounds.

Organic compounds are defined as compounds that contain at least two different elements, as you would expect for any compound, but for an organic compound, at least one of those has to be carbon.

The definition underscores the central role of carbon in the composition of organic compounds due to its ability to form stable covalent bonds with a wide variety of elements, including itself.

The inclusion of hydrogen in addition to carbon is very common for organic compounds given hydrogen's prevalence and its ability to form stable covalent bonds with carbon atoms. However, there are exceptions to this rule.

Not all compounds that contain carbon are classified as organic.

For example, substances like carbon dioxide, CO2, are not typically considered organic compounds despite the fact that they contain carbon atoms. This distinction is based on the type of bonding and structural context into which carbon appears.

And in carbon dioxide, whilst carbon is involved and is bonded to oxygen, this is classed as an inorganic substance because it lacks the complex carbon-centric structure that we would normally expect in an organic molecule.

Don't worry about this difference.

You're not expected at this stage to really understand the nuances between inorganic and organic compounds, but I'm highlighting for you here that there are exceptions to this definition, as there are to a lot of the rules within chemistry.

So, quickly, true or false? An organic compound contains only carbon atoms. What do you think? Well, this is false.

Which of these reasons given below do you think is the best explainer as to why this is a false statement? Pause now to have a think, and press play when you are ready to continue.

Well, compounds by definition must contain two or more different elements.

And so for organic compounds, we would expect that to be true too, and we know one of them must be carbon.

So organic compounds exhibit a vast diversity in their structures, which we talked about several times already, and this can be broadly categorised into two main types based on the arrangement of their carbon atoms, straight, branched, and ring structures.

So straight-chain molecules feature a linear sequence of carbon atoms, with each carbon atom typically bonded to one or two other carbons in a continuous chain.

These molecules may vary in length and may include various different functional groups, which we'll talk about in later lessons, attached along the chain.

But the core structure remains linear.

Branched-chain molecules are similar to straight-chain.

However, these have branching chains, as the name suggests, creating a much more complex structure.

And ring structures, very similar, but obviously have a nice ring structure.

Not too much more to say about that one.

Organic compounds, whilst primarily consisting of carbon and hydrogen, frequently incorporate other elements, such as oxygen and nitrogen.

The inclusion of these elements allows for the formation of a wide range of functional groups, which significantly diversify the physical and chemical properties of organic molecules.

Oxygen and nitrogen in particular are crucial for the structure and function of compounds found in living organisms. For example, alanine, which is an example of an amino acid, contains carbon, hydrogen, oxygen, and nitrogen.

It is a building block of proteins, contributing to their structure and function within cells.

Guanine is one of the four nucleobases in the nucleic acids of DNA and RNA, and is composed of carbon, hydrogen, oxygen, and nitrogen as well.

The presence of oxygen and nitrogen in organic compounds like alanine and guanine highlights their essential roles in biological processes.

The elements contribute to the complexity and functionality of biomolecules supporting the vast array of life processes.

In addition to naturally occurring organic compounds, a significant number of synthetic organic compounds are produced through controlled chemical reactions in laboratories or on an industrial scale.

These synthetic compounds are designed and manufactured to possess specific properties or functionalities that may not be readily available in nature.

Polymers are a prime example of synthetic organic compounds as they consist of very long chains of carbon atoms that can include thousands of repeating units known as monomers.

These monomers can be purely hydrocarbon-based, so contain only hydrogen or carbon atoms, or they may contain other elements such as oxygen, nitrogen, sulphur, or silicon, or many others, leading to a vast diversity of polymer types with varying properties.

Polymers have a wide range of applications, from everyday household items like plastics and textiles to specialised uses in medicine, technology, and engineering.

In this diagram, the monomer shown is ethene, C2H4, a simple organic molecule with a double bond between the carbon atoms. During the polymerization process, this double bond breaks open, allowing the carbon atoms to connect with other ethene molecules.

This reaction repeats with countless ethene molecules, leading to a long chain of carbon atoms, each bonded to hydrogen atoms as well.

The little n denotes the number of repeating units.

As n increases, so does the length of the polymer chain.

The tremendous variety of compounds that carbon can form is organised by grouping these chemicals into families of organic compounds.

These families are characterised by having similar chemical and physical properties.

For instance, methane is a simple hydrocarbon, a molecule that contains only hydrogen and carbon atoms. This is the simplest of what is known as the alkane family.

It includes compounds with only single carbon-carbon bonds.

Propene belongs to the alkene family, which contains at least one carbon-carbon double bond.

Ethanol is part of the alcohol family, and it's characterised by having what's known as a hydroxyl group.

That's the OH that you can see in the structure.

This is known as a functional group and is key to the alcohol family.

Organising carbon compounds into families like alkanes, alkenes, and alcohols allows for a systematic study and understanding of their properties, reactivities, and roles in various applications, ranging from energy sources to solvents and more.

This categorization is crucial for the field of organic chemistry, facilitating the prediction of behaviour and properties of unfamiliar compounds based on known families.

So, here are four statements about organic compounds.

Pause the video now to decide whether they are true.

When you're ready, press play to move on.

So, other than statement B, these are actually all correct statements.

Organic compounds can exist as rings as well as short and long and branched chains.

They often contain atoms like hydrogen, oxygen, and nitrogen.

Here are another four statements, and again, pause the video to decide which are true.

Then press play when you're ready to move on.

Organic compounds are found in nature, but they also can be manmade.

Polymers are an excellent example of a long-chain organic compound.

And organic compounds do not need to contain oxygen and nitrogen, although many do.

Your final tasks, then, for this lesson are to complete the gap fill here by only using the words organic, carbon, or covalent, and then to explain why carbon is able to form various organic compounds.

Pause the video now to attempt these questions, and press play when you're ready to hear the answers.

So, an organic compound is a compound that contains two or more elements, where one is carbon, held together through covalent bonding.

Substances like carbon dioxide are not usually considered to be organic compounds, and compounds that contain carbon can either be found naturally or produced synthetically.

An example is polymers, which have very long carbon chains.

Well done if you got all those correct.

This task is meant to be challenging, and I can understand if you got a little confused where each word was most relevant.

The answer to the final question could include, then, carbon has four electrons in its outer shell.

It is able to form four covalent bonds with other non-metal atoms, such as hydrogen, nitrogen, and oxygen.

That's not to each of them.

That's in total it can form four covalent bonds.

Carbon can also create a variety of complex structures, including chains, branches, and rings.

And carbon can form large molecules, such as proteins and DNA, we call these macromolecules, essential for life as well as synthetic materials, such as polymers.

Some organic molecules which contain carbon are alkanes, alkenes, and alcohols.

Well done for your hard work on this topic today.

Together, we've learned that carbon atoms will form up to four covalent bonds as they will fill their outer shell with four more electrons.

We've also learned that carbon atoms can combine with other non-metal atoms to make a wide range of different molecules, some with rings and some with chains.

An organic compound contains two or more elements, including carbon, and a lot of organic compounds also include hydrogen, oxygen, and nitrogen.

Organic compounds can be both found in nature but also can be produced synthetically.

You've done really well today, and I look forward to seeing you in the next lesson.