Question

Which one of the following is not the characteristic property of carbon? (a) It exhibits catenation. (b) It forms compounds with multiple bonds. (c) Its melting point and boiling point are exceptionally high. (d) It shows semi-metallic character.

Short answer

The characteristic property of carbon that is not correct is (d) It shows semi-metallic character.

Step-by-step solution

Understanding Catenation

Catenation refers to the ability of an element to form bonds with other atoms of the same element. Carbon is well known for forming long chains and rings of carbon atoms, hence, it exhibits catenation.

Recognize Multiple Bonds Formation

Carbon is capable of forming double and triple bonds with various elements, including itself. Compounds like ethene (C2H4) with a double bond, and ethyne (C2H2) with a triple bond, are common examples.

Analyzing Melting and Boiling Points

Carbon, in its standard form as graphite or diamond, does have a high melting point and boiling point, but it does not follow that all carbon compounds have exceptionally high melting and boiling points. Simple carbon compounds can have quite low melting and boiling points.

Examining Semi-metallic Character

Carbon is a non-metal. It does not exhibit semi-metallic properties like conductivity in its standard state, whereas semi-metals are elements that have properties of both metals and non-metals.

Identification of Incorrect Characteristic

By evaluating the properties and characteristics given in options (a), (b), and (c), and knowing that carbon is a non-metal, the statement that does not represent a characteristic property of carbon is (d) It shows semi-metallic character.

Key concepts

Catenation

Carbon's capability to connect with other carbon atoms to form long chains and ring structures is termed as catenation. This unique feature stems from the extraordinary strength of the carbon-carbon bond. Organic chemistry is fundamentally built on this principle, as it allows the formation of an extensive variety of molecular structures ranging from simple hydrocarbons, like methane (CH₄), to immense and complex macromolecules, such as proteins and DNA.

Catenation is not limited only to forming straight chains; carbon atoms can create branched chains and rings, giving rise to a virtually unlimited number of compounds. This diversity is one of the reasons why carbon-based life is so varied and intricate. To enhance understanding, students might find it helpful to visualize or model the chains that carbon atoms create, which can aid in grasping the three-dimensional aspect of molecular structures.

Multiple Bonds in Carbon Compounds

Carbon is versatile in its bonding capabilities, not only forming single bonds but also engaging in multiple bonding. This involves double and triple bonds, contributing to the formation of a wide assortment of compounds with different physical and chemical properties.

For instance, ethene (C₂H₄), which contains a double bond, and ethyne (C₂H₂), with a triple bond, illustrate the difference in bonding. These types of bonds affect the compounds' reactivity and are pivotal in the study of organic chemistry. Multiple bonds allow for the formation of various functional groups such as alkenes and alkynes, which are the building blocks for many other types of carbon-based molecules. Understanding the nature of these bonds is crucial for students learning about organic reactions and synthesis.

Melting and Boiling Points of Carbon Compounds

While elemental carbon, found in forms like diamond and graphite, has high melting and boiling points, it is a misunderstanding to generalize this attribute to all carbon compounds. Many carbon compounds such as alkanes, alcohols, and organic acids have relatively low melting and boiling points, largely due to the molecular forces between these molecules rather than the strength of the carbon bond itself.

Factors that influence these temperatures include molecular weight, polarity, and the presence of functional groups. For example, as the chain length of an alkane increases, so does its melting and boiling point. When explaining these principles, it helps to discuss how different intermolecular forces like hydrogen bonding, dipole-dipole interactions, and London dispersion forces play a role in determining these physical properties.

Semi-metallic Character of Elements

The semi-metallic character is an attribute found in certain elements that exhibit properties of both metals and non-metals. Carbon, however, is classified as a non-metal and typically does not demonstrate semi-metallic properties. Semi-metals or metalloids, like silicon and germanium, find their place on the periodic table along the metal-nonmetal boundary and are characterized by their ability to conduct electricity better than non-metals but not as well as metals.

These elements are essential in the semiconductor industry, which is the cornerstone of modern electronic devices. Students may find it useful to relate the semi-metallic character to real-life applications, such as the use of silicon in computer chips, to better understand its significance.