Important trends and anomalous behavior of Carbon

Introduction

Carbon is a crucial element for most of what makes up a big chunk of chemistry. Organic chemistry, which makes up about a third of the subject itself, revolves around the single element carbon. This shows the vital importance of carbon in this specific field. Apart from its importance in organic chemistry, carbon sticks out as an important part of inorganic chemistry as we’re going to dig a little deeper into understanding its role in Group 14 elements and some of its properties and anomalous behaviors. This will help better understand its role in different kinds of chemical bondings, forming unique structures and why/how does it happen with carbon uniquely?

Body

Carbon is the first member of the 14th group of the elemental table. While it shares a lot of features and properties that are similar to the other elements in the same group, some peculiarities are only to be found in the carbon element alone. 

Now, we shall discuss some of the properties of carbon that make it unique.

Hardness

Carbon is known to harness the hardest substance in the world, which is diamond, a special form of carbon. All the other elements in the same family are soft and fragile. Even one form of carbon, graphite, is soft. But then why does diamond the hardest one might ask?

The answer lies in the structural arrangement of carbon atoms in both scenarios. In the case of graphite, the arrangement of carbon atoms is in such a way that layers of 2D flat carbon sheets are stacked on top of each other with no significant bond between any of the two adjacent layers.

In the case of diamonds, the concept of layers doesn’t exist. Rather, the carbon atoms in the structure are at equal distances from each other and form an interlinked bond. This tetra-valency of carbon allows a single atom of carbon to make four bonds spontaneously. This also allows for a more strengthened bond among all the carbon atoms present in the diamond.

Melting and boiling point

The melting and boiling temperatures of Group 14 elements (the carbon family) are substantially higher than those of Group 13. Because of weaker atomic interactions within bigger molecules, melting and boiling temperatures in the carbon family tend to drop as one progresses down the group. The melting point of lead, for example, is so low that it may readily be liquefied by a flame.

High electronegativity

The electronegativity of group 14 elements is greater than that of group 13 elements. As you progress from C to Si, the electronegativity drops until it reaches a nearly constant value for the remaining elements.

Catenation

Carbon atoms have a natural inclination to build chains and rings by forming covalent connections with one another. Catenation is the term for this characteristic. Because C—C bonds are extremely strong, this is the case. As the size of the group grows larger, the electronegativity drops, and the likelihood to demonstrate catenation reduces. Bond enthalpy values clearly demonstrate this. C > > Si > Ge > Sn is the catenation order. Catenation does not occur in lead.

Carbon may take on allotropic forms due to its catenation and bond-forming properties.

Allotropes

Carbon comes in a variety of allotropic shapes, including crystalline and amorphous forms. The crystalline forms of carbon diamond and graphite are well-known. H.W.Kroto, E.Smalley, and R.F.Curl discovered the third type of carbon, known as fullerenes, in 1985. In 1996, the Nobel Prize was given to them for their discovery.

Atomic and Ionic Radii

Dropping down the periodic table in the carbon family increases atomic and ionic radius while decreasing electronegativity and ionization energy. Due to the inclusion of an extra electron shell as one progresses down the group, the size of the atom rises.

Chemical Properties

Oxidation states and trends in chemical reactivity

The group 14 elements contain four electrons in their outermost shell and are divided into two oxidation states, +4 and +2. In general, molecules in the +4 oxidation state are covalent and can form complexes by receiving electron pairs from donor species. The number of electrons surrounding the core atom in a molecule (e.g., carbon in CCl4) is eight in the tetravalent state, and they are generally not anticipated to operate as electron acceptors or donors.

• Reactivity towards oxygen

When heated in oxygen, all components produce oxides. The most common oxides are monoxide and dioxide, which have the formulas MO and MO2, respectively. Only at extremely high temperatures does SiO exist. Higher oxidation state elements have more acidic oxides than those with lower oxidation states. CO2, SiO2, and GeO2 are acidic gasses, but SnO2 and PbO2 are amphoteric gasses.

CO is a neutral monoxide, while GeO is an acidic monoxide, and SnO and PbO are amphoteric monoxides.

• Reactivity towards water

Water has no effect on carbon, silicon, or germanium. Tin decomposes steam to produce hydrogen gas and dioxide.

             Sn+ 2 H2O  (heat) →   SnO2 + 2 H2

           Water has little effect on lead, owing to the creation of a protective oxide covering.

• Reactivity towards halogen

Even though some elements, such as Ge, Sn, and Pb, can form dihalides, group 14 elements create halides with the typical formula MX4 (CCl4, SiCl4, GeCl4, SnCl4, PbCl4) (MX2). Carbon tetrahalides, such as CCl4, cannot be hydrolyzed owing to the lack of unoccupied valence d-orbitals, although other tetrahalides may.

Silicon Halides 

Silicon combines with halogens to produce SiX4 compounds, where X is any common halogen. SiF4 is a colorless gas, SiCl4 is a colorless liquid, SiBr4 is a colorless liquid, and SiI4 produces colorless crystals at ambient temperature. SiF4 and SiCl4 can both be hydrolyzed entirely, however, SiBr4 can only be partly hydrolyzed.

Metal Halides

Metals in Group 14 include lead and tin. Tin exists in two forms: SnO2 and SnO4. Tinstone contains SnCl2, a good reducing agent. SnF2 was originally employed as a toothpaste component, but NaF has since taken its place.

Conclusion

Carbon differs from the other members of its group in the same way that the other first elements do. Carbon acts differently than other members of its group even though they are on the same ground. Carbon possesses distinct characteristics, which are mostly responsible for its unusual behavior.

• Carbon atoms are quite tiny
• The electronegativity of carbon is quite high
• Carbon has a very high ionization enthalpy
• In the carbon atom, the d orbitals aren’t available