Question

Carbon and silicon belong to IVA group. The maximum coordination number of carbon in commonly occurring compounds is 4, whercas that of silicon is 6 . This is duc to (1) Large size of silicon (2) Availability of vacant d-orbitals in silicon (3) Morc clectropositive nature of silicon (4) Silicon being vulnerable to attack by nucleo philic reagents

Short answer

Option (2) Availability of vacant d-orbitals in silicon

Step-by-step solution

Understand Coordination Number

The coordination number of an atom in a molecule refers to the number of atoms directly bonded to it. For carbon, this number is 4 in common compounds.

Compare Carbon and Silicon

Both carbon and silicon are in the same group (group IVA) of the periodic table. However, silicon can have a coordination number of up to 6 in some compounds.

Analyze Options

Consider why silicon can exceed the coordination number of carbon. Evaluate each option:1. Large size of silicon2. Availability of vacant d-orbitals in silicon3. More electropositive nature of silicon4. Silicon being vulnerable to attack by nucleophilic reagents

Availability of Vacant d-Orbitals

Silicon has vacant d-orbitals that can be used for bonding, allowing it to expand its coordination number to 6. Carbon does not have these vacant d-orbitals and thus cannot exceed a coordination number of 4.

Key concepts

Carbon and Silicon

Carbon and silicon are both crucial elements in chemistry and share the same group in the periodic table: Group IVA. Carbon is fundamental for life, being a key component of organic molecules like DNA and proteins. Silicon, on the other hand, is famous for its role in technology, especially in making semiconductors for computers.

One major difference between these two elements is their size. Carbon atoms are smaller than silicon atoms, affecting their chemical properties. For instance, carbon's small size allows it to form strong double and triple bonds. In contrast, silicon's larger size makes such bonding less favorable. Instead, silicon often forms bonds with more atoms.

Moreover, silicon can access more electron orbitals than carbon, enabling it to have a higher coordination number. In simple terms, this means silicon can connect to more atoms in a molecule compared to carbon. To put it into perspective, the coordination number for silicon can reach up to 6, while carbon mostly sticks to 4.

Group IVA Elements

Carbon and silicon belong to the same group in the periodic table, known as Group IVA. This group also includes germanium, tin, and lead. All these elements have four electrons in their outermost shell, which means they can form four bonds with other elements.

One thing that makes Group IVA elements interesting is how their properties change as you go down the group. Starting with carbon, the smallest and lightest, each subsequent element is larger and heavier. This increase in size leads to different behavior in chemical reactions. For example, carbon is known for forming multiple strong bonds in organic compounds, while silicon often forms network structures in silicates and minerals.

Additionally, the ability of these elements to form compounds varies. Carbon is incredibly versatile and can make a wide range of compounds, from simple molecules like methane (CH₄) to complex polymers. Silicon also forms many compounds but primarily bonds with oxygen to create various silicates.

Vacant d-orbitals

One key reason why silicon can have a higher coordination number than carbon is because of its vacant d-orbitals. But what exactly are vacant d-orbitals?

In atoms, electrons are arranged in a series of shells and subshells. These include s, p, d, and f orbitals. For silicon, after the 3s and 3p orbitals are filled, the 3d orbitals remain empty and are referred to as 'vacant.' These vacant d-orbitals can participate in bonding with other atoms, allowing silicon to bond with more atoms than carbon can.

Carbon lacks these d-orbitals because its outermost shell is the 2nd shell, which doesn't have d-orbitals. As a result, carbon's coordination number maxes out at 4. Silicon, with its additional orbitals, can accommodate more atoms, leading to a coordination number of up to 6. This property makes silicon versatile in forming complex structures, especially in minerals and industrial materials.