MUSLIM SCHOLAR. 1

CARBON AND ITS COMPOUNDS.

The chemical substances which consist of carbon are called carbon compounds. the compounds which have single bonds are called saturated compounds. Compounds of carbon with double bonds and triple bonds are called unsaturated compounds.

Note: Double bond contains 1 sigma bond and 1 pie bond.

           Triple bond contains 1 sigma bond and 2 pie bonds. 

 

Ionic Bond.

The electrostatic force of attraction between the oppositely charged ions of the atom holds the compound together with the bond called an ionic bond. Ionic bond involves the transfer of valence electrons, between a metal and a nonmetal. Ionic compounds are crystalline solids (made of ions) that possess high melting and boiling points. They conduct electricity in a solution and molten state. They are soluble in water and polar solvents.

 

Covalent Bond.

The bond which is formed when pairs of electrons are shared between two atoms is called a covalent bond. It is usually formed between two same non-metallic atoms or between non-metallic atoms with similar electronegativity. Such compounds are called diatoms. 

Covalent Bonding.

If the carbon atom loses four of its valence electrons, to attain its nearest stable electronic configuration i.e, a huge amount of energy is involved. C⁴⁺ ion hence formed will be highly unstable due to the presence of six protons and two electrons.

If the carbon atom gains four electrons to get the nearest electronic configuration of the noble gas, Ne, C⁴⁻ ion will be formed. But again, a huge amount of energy is required for C⁴⁺ ions it is difficult for 6 protons to hold 10 electrons. Hence, to satisfy its tetravalency, carbon shares all four of its valence electrons and forms covalent bonds.

Lewis Dot Structure.

Lewis structures are also known as Lewis’s dot structures or electron dot structures.

 These are diagrams with the element’s symbol in the centre. The dots around it represent the valence electrons of the element.

Lewis structures of elements with atomic numbers 6, 7, 8.

Covalent Bonding in H₂, N₂, and O₂.

Formation of a single bond in a hydrogen molecule:

Hydrogen atomic number is 1 and its electronic configuration is 1s¹. Each hydrogen atom has a single electron in the valence shell. It requires one more to attain the nearest noble gas configuration (He). Hence both atoms share one electron each to form a single bond. It is represented by a single line between the two atoms.

 

 

Formation of a double bond in an oxygen molecule:

          The oxygen atomic number is 8 and its electronic configuration is 1s²,2s²,2p⁴. Each oxygen atom has six electrons in the valence shell (2, 6). It requires two electrons to attain the nearest noble gas configuration (Ne). Hence, both atoms share two electrons each and form a double bond. It is represented by double lines between the two atoms.

Formation of a triple bond in a nitrogen molecule:

          Nitrogen atomic number is 7 and its electronic configuration is 1s²,2s²,2p³. Each nitrogen atom has five electrons in the valence shell (2, 5). It requires three electrons to attain the nearest noble gas configuration (Ne). Hence, both atoms share three electrons each and form a triple bond. It is represented by triple lines between the two atoms.

Single, Double, and Triple Bonds and Their Strengths.

Bond strength:

      The bond strength of a bond is determined based on the amount of energy required to break the bond. It signifies that the energy required to break three bonds is higher than that for two bonds or a single bond.

 Order of Bond: Triple bond>double bond>single bond

Bond length:

      Bond length is determined by the distance between nuclei of the two atoms in a bond. The distance between the nuclei of two atoms is the least when they are triple-bonded.

  Order Of Bond Length: Triple bond<double bond<single bond.

Covalent Bonding of N, O with H and Polarity.

Ammonia.

In ammonia (NH₃), the three hydrogen atoms share one electron each with the nitrogen atom and form three covalent bonds. Ammonia has one lone pair. All three N-H covalent bonds are polar. It forms a shape of trigonal pyramidal and the bond angle is 107’.

 

N atom is more electronegative than the H atom. Thus, the shared pair of electrons lies more towards N atom which causes the N atom to acquire a slightly negative charge and H atom a slightly positive charge.

 

 Water.

In water (H₂O), the two hydrogen atoms share one electron each with the oxygen atom and form two covalent bonds. Water has two lone pairs of electrons. It forms an angular (or) V shape whose bond angle is 104.5’.

The two O-H covalent bonds are polar in nature, a hydrogen bond is formed between 2 molecules of water. ​​​​​​O atom is more electronegative than the H atom. Thus, the shared pair of electrons lies more towards O atom which causes the O atom to acquire a slightly negative charge and H atom a slightly positive charge.

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Covalent Bonding in Carbon.

A methane molecule (CH₄) is formed when four electrons of carbon are shared with four hydrogen atoms as shown below. It forms a shape tetrahedral with a bond angle of 109.5’ and a bond length is 108.7pm.

Catenation occurs most readily with carbon due to its small size, electronic configuration, and unique strength of carbon-carbon bonds. Tetravalency, catenation and the tendency to form multiple bonds with other atoms account for the formation of innumerable carbon compounds.

Catenation.

Catenation is the property of an element that forms covalent bonds with the other atoms of the same element to form a series of straight or branched chains and rings of different sizes.

Examples; carbon, sulphur, and silicon.

Carbon.

Organic compounds are formed by the combination of Hydrogen, oxygen, carbon, few elements. They are significantly more numerous than inorganic compounds that do not form bonds. Carbon has tetravalency, and Catenation It forms single, double, and triple bonds demonstrates its versatility. It forms straight chains, branching chains, and rings when joined to other carbon atoms.

Carbon is a chemical element whose symbol C and its atomic number 6 which is a versatile element that can be found in a wide variety of chemical combinations. The property of carbon elements due to which its atom can join one another to form long carbon chains is called catenation.

 

Melting point, Boiling point, and Electrical Conductivity of covalent compounds.

They are molecular compounds that are present as gases, liquids or solids. They have weak intermolecular forces, with low melting and boiling points. They possess poor electrical conductors in all phases specifically in solution or molten state. They are mostly soluble in nonpolar liquids.

 

Allotropes of Carbon.

The phenomenon of the existence of the same element in different physical forms with similar chemical properties is known as allotropy.

 Example: carbon, Sulphur, phosphorus, etc.

• Amorphous allotropes of carbon include coal, coke, charcoal, lamp black.
• Crystalline allotropes of carbon include diamond, graphite, and, fullerene.

 

Diamond.

Diamond has a regular tetrahedral geometry because each carbon is connected to four neighboring carbon atoms with a single covalent bond, which forms in a single unit of a crystal. These crystal units lie in different planes and are connected to each other, forms a rigid three-dimensional cubic pattern of the diamond.

• Diamond is a good conductor of heat.
• They are poor conductor of electricity.
• They possess very high refractive index of 2.5. 
• They have high density of 3.5g/cc.
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Graphite.

In graphite, each carbon atom is bonded covalently to three other carbon atoms, leaving each carbon atom with one free valency. This arrangement results in hexagonal rings in a single plane and such rings are stacked over each other through weak Van der Waals forces.

Graphite is a good conductor of electricity which shows a soft and slippery structure whose a density of 2.25 g/cc.

C_60.

It is the most common naturally occurring fullerene also known as Buckminsterfullerene, which is the very popular and stable form of the known fullerenes. It is found in small quantities in soot. It consists of 60 carbon atoms arranged in 12 pentagons and 20 hexagons, like in a soccer ball.

S₈

In its native state, sulphur show catenation of up to 8 atoms in the form of S8 molecule. It has a puckered ring structure.