Carbon and Its Various Forms Archives

1. Which one among the following elements has the highest catenation

Which one among the following elements has the highest catenation property?

Silicon

Carbon

Nitrogen

Oxygen

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UPSC CISF-AC-EXE – 2024

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Catenation is the ability of an element to form bonds with atoms of the same element. Carbon has the strongest tendency for catenation among all elements. This property allows carbon atoms to link together to form long chains, branched structures, and rings, forming the backbone of the vast number of organic compounds.

Carbon exhibits the highest catenation property among elements, forming diverse organic structures.

Silicon also shows catenation, forming silanes (Si-Si bonds), but the Si-Si bond is weaker than the C-C bond, limiting the length and stability of silicon chains compared to carbon chains. Nitrogen can form chains (e.g., in hydrazine, N₂H₄), but N-N bonds are relatively weak. Oxygen primarily forms chains of two atoms (O-O bond in peroxides), and longer chains are generally unstable. The high strength of the C-C bond and carbon’s ability to form multiple bonds (single, double, triple) contribute to its exceptional catenation ability.

2. Graphite is a good conductor of electricity. It is because of its

Graphite is a good conductor of electricity. It is because of its

linear structure

tetrahedral structure

triangular planar structure

hexagonal multilayer structure

This question was previously asked in

UPSC CISF-AC-EXE – 2018

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Graphite is a good conductor of electricity because of its structure. It consists of layers of carbon atoms arranged in a hexagonal lattice. Within each layer, carbon atoms are bonded covalently, with each carbon atom bonded to three others. This $sp^2$ hybridization leaves one unhybridized p-orbital per carbon atom, which overlaps with adjacent p-orbitals to form a delocalized pi electron system across the entire layer. These delocalized electrons are mobile and can carry electric charge, making the layers conductive. The overall structure is described as hexagonal multilayer, which creates the environment for these delocalized electrons.

The electrical conductivity of graphite is due to the presence of delocalized electrons in its layered hexagonal structure.

The layers in graphite are weakly bonded by Van der Waals forces, allowing them to slide easily, which is why graphite is soft and used as a lubricant. This contrasts with diamond, which has a rigid tetrahedral structure with all valence electrons localized in sigma bonds, making it an electrical insulator.

3. The common element in graphite, fullerene, diamond and graphene is :

The common element in graphite, fullerene, diamond and graphene is :

Oxygen

Nitrogen

Hydrogen

Carbon

This question was previously asked in

UPSC CAPF – 2023

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Graphite, fullerene, diamond, and graphene are all different structural forms of the element carbon. They are known as allotropes of carbon. Diamond has a tetrahedral structure, graphite has a layered hexagonal structure, fullerenes are cage-like molecules (e.g., C60), and graphene is a single layer of carbon atoms arranged in a hexagonal lattice. Therefore, the common element in all of them is carbon.

Allotropes are different structural modifications of an element; the atoms are bonded together in a different manner. Diamond, graphite, fullerenes, and graphene are allotropes of carbon.

The different structures of carbon allotropes result in vastly different physical and chemical properties. For instance, diamond is extremely hard and an electrical insulator, while graphite is soft and a good electrical conductor.

4. Which one of the following statements is not correct ?

Which one of the following statements is not correct ?

Graphite is a non-metal

Graphite is an allotrope of carbon

Graphite is a conductor of electricity

Graphite has a tetrahedral structure

This question was previously asked in

UPSC CAPF – 2016

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Statement D is incorrect. Graphite has a layered structure where carbon atoms are arranged in hexagonal rings. Each carbon atom is covalently bonded to three other carbon atoms within the same layer. These layers are held together by weak van der Waals forces. A tetrahedral structure is characteristic of diamond, another allotrope of carbon, where each carbon atom is bonded to four other carbon atoms in a three-dimensional network.

Distinguishing between the structures of different allotropes of carbon like graphite and diamond is fundamental in chemistry and materials science.

Statement A is correct: Graphite is an allotrope of carbon, which is a non-metal element.
Statement B is correct: Graphite is one of the naturally occurring allotropes of carbon.
Statement C is correct: Graphite is a good conductor of electricity due to the presence of delocalized electrons within its layered structure, which can move freely along the layers.

5. Which one among the following is not a form of carbon?

Which one among the following is not a form of carbon?

Graphene

Graphite

Fullerene

Quartz

This question was previously asked in

UPSC CAPF – 2013

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D) Quartz

Allotropes are different structural modifications of an element in the same physical state.
– Graphene, Graphite, and Fullerene are all allotropes of carbon. Graphene is a single layer of carbon atoms in a hexagonal lattice. Graphite is composed of multiple layers of graphene stacked together. Fullerenes are carbon molecules forming hollow spheres, ellipsoids, or tubes (like buckyballs).
– Quartz, on the other hand, is a mineral composed of silicon and oxygen, with the chemical formula SiO2 (silicon dioxide). It is a major component of the Earth’s crust. Therefore, quartz is not a form of carbon.

Other common allotropes of carbon include diamond and amorphous carbon. The different physical properties of these allotropes (e.g., hardness, conductivity) are due to the different ways the carbon atoms are bonded together.

6. Diamond is a polymorph of graphite. Both contain carbon atoms, but the

Diamond is a polymorph of graphite. Both contain carbon atoms, but they have extremely different properties because of the condition in which they are formed. Diamond is obtained after applying

very high pressure and low temperature

very low pressure and high temperature

very low pressure and low temperature

very high pressure and high temperature

This question was previously asked in

UPSC CAPF – 2013

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The correct option is D. Diamond is formed under conditions of very high pressure and high temperature deep within the Earth’s mantle.

Diamond and graphite are both allotropes (polymorphs) of carbon. Their dramatically different properties (hardness, electrical conductivity, etc.) arise from their different crystal structures, which are formed under vastly different pressure and temperature conditions. Graphite is the stable form of carbon at standard conditions, while diamond is stable only at extremely high pressures and temperatures.

Natural diamonds are formed at depths of 140 to 190 kilometers (87 to 118 miles) in the Earth’s mantle, where pressures are between 45 and 60 kilobars and temperatures are between 900 and 1,300 degrees Celsius (1,650 to 2,370 degrees Fahrenheit). Synthetic diamonds are also created using high-pressure high-temperature (HPHT) or chemical vapor deposition (CVD) methods, simulating similar extreme conditions.

7. The elemental composition of diamond is

The elemental composition of diamond is

Carbon and Hydrogen

Carbon and Oxygen

Pure Carbon

Pure Silicon

This question was previously asked in

UPSC NDA-2 – 2024

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Diamond is an allotrope of carbon. This means it is a form of pure carbon where the carbon atoms are arranged in a specific crystal structure (a tetrahedral lattice). Therefore, diamond consists solely of carbon atoms and no other elements. Graphite is another well-known allotrope of pure carbon.

Allotropes are different structural modifications of an element. Diamond is a crystalline allotrope of carbon.

In diamond, each carbon atom is covalently bonded to four other carbon atoms in a rigid, three-dimensional tetrahedral network. This structure makes diamond extremely hard and gives it a high melting point.

8. Which among the following statements with respect to carbon is/are cor

Which among the following statements with respect to carbon is/are correct ?

1. Carbon forms the basis for all living organisms and many things we use
2. Carbon shows tetra-valency and the property of catenation
3. Carbon forms covalent bonds with itself and other elements
4. Carbon forms compounds containing triple and tetra bonds between carbon atoms

Select the correct answer using the code given below :

1 only

1 and 2 only

1, 2 and 3

2 and 4

This question was previously asked in

UPSC NDA-2 – 2023

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Statements 1, 2, and 3 are correct. Carbon forms the backbone of all organic life and is present in countless materials we use (statement 1). Carbon has four valence electrons, allowing it to form four covalent bonds (tetra-valency), and it can bond with itself to form long chains or rings (catenation) (statement 2). Carbon forms covalent bonds not only with itself but also with other elements like hydrogen, oxygen, nitrogen, etc. (statement 3). Statement 4 is incorrect; carbon forms single, double, and triple bonds with other carbon atoms but not stable tetra (quadruple) bonds in typical organic chemistry contexts.

Carbon’s unique properties of tetra-valency and catenation, and its ability to form strong covalent bonds, are fundamental to organic chemistry and the diversity of carbon compounds. Carbon forms single, double, and triple bonds, but not quadruple bonds, between carbon atoms in stable molecules.

The vast number of carbon compounds makes organic chemistry a distinct branch of chemistry. Catenation is particularly strong in carbon, enabling the formation of complex molecular structures. While theoretical studies have explored the possibility of quadruple bonds in some exotic carbon species, they are not characteristic of carbon bonds in everyday substances.

9. Buckminster fullerene, which looks like a football, is an allotropic f

Buckminster fullerene, which looks like a football, is an allotropic form of

Phosphorus

Sulfur

Carbon

Tin

This question was previously asked in

UPSC NDA-2 – 2023

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Buckminster fullerene, which looks like a football, is an allotropic form of Carbon.

Allotropes are different structural modifications of an element. Carbon exists in several allotropic forms, including diamond, graphite, graphene, and fullerenes. Buckminster fullerene, also known as C60, is the most well-known fullerene molecule, consisting of 60 carbon atoms arranged in a spherical structure resembling a soccer ball (truncated icosahedron).

Fullerenes were discovered in 1985 by Robert Curl, Harold Kroto, and Richard Smalley, who were awarded the Nobel Prize in Chemistry in 1996 for their work. Other allotropes of carbon like diamond and graphite are well-known for their distinct physical properties arising from different atomic arrangements. Phosphorus, Sulfur, and Tin also have allotropes, but fullerenes are specific to Carbon.

10. Which one of the following statements is NOT correct ?

Which one of the following statements is NOT correct ?

Buckminsterfullerene is an allotrope of carbon

Diamond is a good conductor of electricity

Graphite is a good conductor of electricity

In graphite, each carbon atom is linked to three other carbon atoms

This question was previously asked in

UPSC NDA-2 – 2020

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The statement which is NOT correct is (B) Diamond is a good conductor of electricity. Diamond has a structure where each carbon atom is bonded to four other carbon atoms via strong covalent bonds. All valence electrons are tightly held in these bonds, meaning there are no free electrons to carry charge. Therefore, diamond is a poor conductor of electricity (a good electrical insulator).

Electrical conductivity in materials depends on the presence of free charge carriers, such as free electrons. The arrangement and bonding of atoms determine the availability of these carriers.

Statement (A) is correct: Buckminsterfullerene (C60) is a form of carbon, belonging to the fullerene family, which are allotropes of carbon. Statement (C) is correct: Graphite conducts electricity because each carbon atom is bonded to three others, leaving one delocalized electron per atom that can move throughout the layers. Statement (D) is correct: In graphite, carbon atoms are arranged in hexagonal layers where each carbon is covalently bonded to three other carbon atoms.