Carbon & Its Compounds Chapter Notes - Science Class 10

Did you know that carbon, the foundation of many everyday items, plays a crucial role in our lives? It's found in the food we eat, the clothes we wear, and even the medicines we take. In fact, all living structures are carbon-based! But why is carbon so significant?
In this EduRev document, we will explore the Chapter Notes that delve into the exceptional properties of carbon, showcasing why it is an invaluable element.

Bonding in Carbon 

Carbon is a fascinating element with a wide range of uses and properties. One of its most important features is its ability to bond with other elements to form various compounds.  Carbon achieves its tetravalency by forming covalent bonds.

Tetravalence of Carbon

• In order for a carbon atom to achieve the electronic configuration of the nearest noble gas, Helium, it would require a significant amount of energy to either lose or gain four valence electrons. 
• If it were to lose four electrons, it would become highly unstable and form an unstable C4+ ion due to the presence of six protons and only two electrons. 
• Similarly, if it were to gain four electrons, it would also require a large amount of energy and form an unstable C4- ion. 
• But, Carbon achieves its tetravalency by forming covalent bonds, wherein it shares all four of its valence electrons. This sharing of electrons enables carbon to attain a stable electronic configuration without requiring excessive energy.
• Let's consider the example of methane (CH₄).

Bonding in Methane

In methane, carbon forms covalent bonds with four hydrogen atoms. Each hydrogen atom contributes one electron, and carbon shares one electron from each of the hydrogen atoms. This sharing of electrons allows carbon to achieve a stable electronic configuration.

What is Covalent Bond?

A covalent bond is formed when pairs of electrons are shared between two atoms. It is primarily formed between two same nonmetallic atoms or between nonmetallic atoms with similar electronegativity.

Covalent Bonding in Hydrogen, Nitrogen and Water

The atoms of other elements like hydrogen, oxygen and nitrogen, chlorine also form bonds by sharing of electrons.

• Hydrogen is the simplest and most abundant element in the universe. It is also a very versatile element with a unique bonding capability. 
• Hydrogen has only one electron in its valence shell, making it highly reactive and able to form strong bonds with many other elements. The most common type of bonding in hydrogen is covalent bonding, where it shares electrons with other elements to form molecules. 
• Hydrogen can also form ionic bonds, where it donates or accepts electrons to form ions. These bonding properties make hydrogen a critical component in many chemical reactions, including those that power the sun and other stars.

H-H Single bond between Hydrogen Atoms(H₂)

• Nitrogen is a vital element found in both organic and inorganic compounds, and its bonding properties are essential to its many applications. 
• Nitrogen has five electrons in its outermost shell, which allows it to form a wide range of bonding arrangements, including covalent, ionic, and metallic bonds. 
• Covalent bonding is the most common type of bond found in nitrogen-containing compounds, where nitrogen shares electrons with other nonmetal atoms to form stable molecules. These compounds have a wide range of applications, from fertilizers to pharmaceuticals

N≡ N Triple bond between Nitrogen atoms

• Water is a unique and essential compound that plays a critical role in many aspects of life on Earth. The bonding in water is a key factor that gives it its distinctive properties. 
• Water molecules consist of two hydrogen atoms covalently bonded to one oxygen atom, forming a V-shaped molecule. 
• The hydrogen atoms are bonded to the oxygen atom by sharing electrons, resulting in a polar covalent bond. This means that the electrons in the bond are not shared equally, with the oxygen atom pulling the electrons closer to itself.

Water molecule has a single covalent between one oxygen and two hydrogen atoms(H₂O)

Physical Properties of Covalent Compounds

• Covalent compounds have low melting and boiling points as they have weak intermolecular forces.
• They are generally poor conductors of electricity as electrons are shared between atoms and no charged particles are formed.

What is Ionic Bond?

Ionic bonding is a type of chemical bond that occurs when there is a transfer of valence electrons, usually between a metal and a nonmetal.

Formation of Ionic Bond in NaCl

• In this process, the metal atom loses one or more electrons to become a positively charged ion, known as a cation, while the nonmetal atom gains those electrons to become a negatively charged ion, known as an anion. The resulting electrostatic attraction between the oppositely charged ions forms an ionic bond.
• For example, consider the formation of sodium chloride (NaCl). Sodium, a metal, has one valence electron in its outermost shell, while chlorine, a nonmetal, requires one electron to complete its octet. 
• In the process of ionic bonding, sodium loses its valence electron to become a sodium cation (Na+), and chlorine gains that electron to become a chloride anion (Cl-). The attraction between the Na+ and Cl- ions leads to the formation of an ionic bond, resulting in the creation of the compound sodium chloride.
• Ionic bonds are characterized by the transfer of electrons and the formation of charged ions. They often result in the formation of crystalline solids and exhibit strong electrostatic forces between the ions.

Versatile Nature of Carbon

Carbon is a unique element in that it has two characteristic properties (Catenation and Tetravalency) that lead to the formation of a large number of compounds. 

Examples of Catenation

1. Catenation: Self-Linking Ability of Carbon Atoms

• Carbon atoms possess the unique ability to form long chains or rings through covalent bonds.
• This allows carbon atoms to bond with other carbon atoms, resulting in linear, branched, or cyclic structures.
• The strong covalent bonds between carbon atoms enable the formation of stable molecules with diverse chemical and physical properties.

2. Tetravalency: Four Valence Electrons

• Carbon atoms have four valence electrons available for bonding.
• This tetravalency enables carbon to form strong covalent bonds with various atoms, including hydrogen, oxygen, nitrogen, and sulphur.
• Carbon can establish single, double, or triple bonds with these atoms, based on the number of available electrons and desired molecular stability.

Versatility and Applications of Carbon Compounds

• The combination of catenation and tetravalency makes carbon an incredibly versatile building block for a wide range of organic molecules, including those found in living organisms.
• Carbon compounds are essential components of numerous important materials, such as plastics, fuels, and medicines.
• The stable, long-chain molecules formed by carbon play a critical role in the field of organic chemistry.
• Carbon's exceptional properties make it a foundation for the creation of diverse compounds, contributing to advancements in various industries and enhancing our understanding of organic chemistry.

Saturated and Unsaturated Carbon Compounds

• Compounds made up of hydrogen and carbon are called hydrocarbons.
• There are two types of Hydrocarbons.
  (i) Saturated Hydrocarbons
  (ii) Unsaturated Hydrocarbons

1. Saturated Hydrocarbons

• Single bond between carbon atoms.
• ㅡCㅡCㅡ
• Alkanes are saturated hydrocarbons.
  General Formula: C_nH_2n+2

2. Unsaturated Hydrocarbons

• Double or triple bond between carbon atoms.
• Alkenes and Alkynes are unsaturated hydrocarbons.
• Alkenes: ㅡC＝Cㅡ
  General formula: C_nH_2n
• Alkynes: ㅡC≡Cㅡ
  General Formula: C_nH_2n-2

Electron Dot Structure of Saturated Hydrocarbons

Ethane C₂H₆

Names, molecular formulae and  condensed structure formulae of saturated hydrocarbons (Alkanes):

Electron Dot Structure of Unsaturated Hydrocarbons

Ethene (C₂H₄)

Ethyne (C₂H₂)

Names, molecular formulae and structure formulae of unsaturated hydrocarbons (Alkenes and Alkynes):

Carbon Compounds on the Basis of Structure

(i) Straight (unbranched) chain

They have a linear arrangement of carbon atoms bonded together with single covalent bonds

Example: C₃H₈

(ii) Branched

These three above compounds have the same molecular formula but different structures called structural isomers and the phenomenon is structural isomerism.

(iii) Cyclic

Cyclic hydrocarbons, also known as cyclic compounds, are organic molecules that contain carbon atoms arranged in a ring structure.

Example: C₆H₁₂

_{Example: Cyclopentane}

Functional Groups

• In the hydrocarbon chain, one or more hydrogen atom is replaced by other atoms in accordance with their valencies. These are heteroatoms.
• These heteroatoms or group of atoms which make carbon compound reactive and decides their properties are called functional groups.

Homologous Series

It is a series of compounds in which some functional group substitutes for the hydrogen in a carbon chain.

Example: Alcohols – CH₃OH, C₂H₅OH, C₃H₇OH, C₄H₉OH

• They have the same general formula.
• Any two homologues differ by – CH₂ group and the difference in molecular mass is 14µ.
• They have the same chemical properties but show a gradual change in physical properties.

Nomenclature of Carbon Compounds

• When naming a carbon compound, the number of carbon atoms in the compound is identified and the name of the basic carbon chain is modified by a prefix or a suffix indicating the nature of the functional group present in the compound.
• The functional group can be indicated by a prefix or a suffix. If the suffix of the functional group begins with a vowel, such as a, e, i, o, u, the final 'e' in the name of the carbon chain is removed and the appropriate suffix is added. For example, a three-carbon chain with a ketone group would be named as propanone.
• If the carbon chain is unsaturated, the final 'ane' in the name of the carbon chain is substituted by 'ene' or 'yne'.
• The names of compounds in a homologous series are based on the name of the basic carbon chain modified by a prefix or a suffix indicating the nature of the functional group.

Chemical Properties of Carbon Compounds

(i) Combustion

• Carbon and its compounds are used as fuels because they burn in the air releasing a lot of heat energy.
• Saturated hydrocarbons generally burn in the air with blue and non-sooty flame.
• Unsaturated hydrocarbon burns in air with a yellow sooty flame because the percentage of carbon is higher than saturated hydrocarbon which does not get completely oxidized in the air.

• C + O₂ → CO₂ + heat and light 
• CH₄ + O₂ → CO₂ + H₂O + heat and light 
• CH₃CH₂OH + O₂ → CO₂ + H₂O + heat and light 

(ii) Oxidation

• Oxidation in carbon compounds refers to a chemical reaction in which a carbon-containing compound loses electrons, resulting in an increase in the oxidation state of carbon. 
• This process involves the gain of oxygen or the loss of hydrogen from the carbon compound, resulting in the formation of new functional groups.
• Alcohols can be converted to carboxylic acid in presence of oxidizing agent alkaline KMnO4 (potassium permanganate) or acidic potassium dichromate.

(iii) Addition Reaction

• Unsaturated hydrocarbon adds hydrogen in the presence of catalyst palladium or nickel. 
• Vegetable oils are converted into vegetable ghee using this process. 
• It is also called hydrogenation of vegetable oils.

(iv) Substitution Reaction

The reaction between chlorine and alkane is an example of this halogenation process. When exposed to sunlight, the chlorine molecules dissociate into highly reactive chlorine radicals, which can abstract hydrogen atoms from the alkane, forming hydrochloric acid (HCl) and a hydrocarbon radical. This hydrocarbon radical can then react with another chlorine molecule, replacing the hydrogen atom with a chlorine atom and forming a chloroalkane.

CH₄ + Cl₂ → CH₃Cl + HCl (in the presence of sunlight)

Ethanol

Physical Properties

• Colourless, pleasant smell and burning taste.
• Soluble in water.
• Volatile liquid with a low boiling point of 351 K.
• Neutral compound.

Chemical Properties

(i) Reaction with Sodium
This reaction is used as a test for ethanol by the evolution of H₂ gas (Burn with pop sound).

2Na + 2CH₃CH₂OH → 2CH₃CH₂O–Na+ + H₂

(ii) Dehydration

Ethanoic acid

Physical Properties

• Colourless liquid having sour taste and have smell of vinegar.
• Boiling point is 391 K.
• When pure CH₃COOH is frozen, it forms a colourless ice-like solid. So it is called glacial acetic acid.

Chemical Properties

(i) Esterification

Sweet-smelling ester is formed

This is saponification as soap is prepared by this

(ii) Reaction with base

NaOH + CH₃COOH → CH₃COONa + H₂O

(iii) Reaction with carbonates and hydrogen carbonates :

2CH₃COOH + Na₂CO₃ → 2CH₃COONa + H₂O + CO₂

CHH₂COOH + NaHCOH₂ → CH₃COONa + H₂O + CO₂

Soaps and Detergents

• Soap is sodium or potassium salt of long-chain carboxylic acid. Example: C₁₇H₃₅COONa⁺
• Soaps are effective only in soft water.
• Detergents are ammonium or sulphonate salt of long chain of carboxylic acid.
• Detergents are effective in both hard and soft water.

A soap molecule has:

(i) Ionic (hydrophilic) part

(ii) Long hydrocarbon chain (hydrophobic) part

Cleansing Action of Soap

Most dirt is oily and the hydrophobic end attaches itself to dirt and the ionic end is surrounded by molecules of water. This results in the formation of a radial structure called micelles. Soap micelles help to dissolve dirt and grease in water and the cloth gets cleaned.

Micelle Formation

• The magnesium and calcium salt present in hard water reacts with soap molecules to form an insoluble product called scum. This scum creates difficulty in a cleansing action.
• By use of detergent, insoluble scum is not formed with hard water and cloths get cleaned effectively.

Frequently Asked Questions (FAQs)

Q1. What is the importance of carbon in organic chemistry?
Ans. Carbon is important in organic chemistry because it can form four covalent bonds with other atoms, including other carbon atoms. This allows for the formation of complex and diverse organic compounds, including those found in living organisms. 

Q2. What are the properties of carbon compounds?
Ans. Carbon compounds typically have low melting and boiling points and are insoluble in water but soluble in organic solvents. They also have varied properties depending on their functional groups, which can affect their reactivity and physical characteristics. 

Q3. How are carbon compounds classified?
Ans. Carbon compounds can be classified based on their functional groups, which are specific arrangements of atoms that determine the compound's properties and reactivity. Common functional groups include alcohols, aldehydes, ketones, carboxylic acids, and amines. 

Q4. What is the difference between saturated and unsaturated carbon compounds?
Ans. Saturated carbon compounds contain only single covalent bonds between carbon atoms and are typically more stable and less reactive than unsaturated compounds. Unsaturated compounds, on the other hand, contain one or more double or triple bonds between carbon atoms and are generally more reactive and less stable.

Q5. How do carbon compounds contribute to climate change?
Ans. Carbon compounds, particularly carbon dioxide, contribute to climate change by trapping heat in the Earth's atmosphere and causing global warming. This is due to the greenhouse effect, which occurs when certain gases, including carbon dioxide, absorb and re-emit heat from the sun, leading to an increase in global temperatures. The burning of fossil fuels, deforestation, and other human activities have greatly increased the concentration of carbon dioxide in the atmosphere, exacerbating the effects of climate change.