Question

Use atomic and molecular properties to explain why life is based on carbon, rather than some other element such as silicon.

Short answer

With four valent electrons, carbon can form bonds with a wide range of atoms (O, H, N, S, Zn, Fe, etc.). The chemicals are quite stable, although they can be metabolised into other useful molecules very ease. However, because silicon forms stronger connections that are more difficult to break, metabolising silicon-based substances would need more energy.

${\mathrm{CO}}_2$is also a gas, therefore it can participate in carbon cycling more easily than${\mathrm{SiO}}_2$, which is a solid.

Step-by-step solution

Element

An element is a substance with the same number of protons in all of its atoms, or the same atomic number in all of its atoms.

Explanation

Carbon possesses six electrons, four of which are valent electrons, and is in the second period, ${14}^{\mathrm{th}}$group. Its electrical structure makes him the ideal atom for bonding a wide range of atoms, such as hydrogen, oxygen, nitrogen, or sulphur in amino acids (protein building blocks), or metal atoms like zinc or iron in organometallic compounds.

Aside from that, while carbon molecules are relatively stable, they are reactive enough to be "transformed" into other compounds in a variety of chemical processes. When you eat food high in proteins, sugar, or fat, for example, your body must first metabolise those molecules into smaller molecules that may be used to produce energy to keep your body working.

Silicon, on the other hand, although having four valent electrons, tends to form stronger connections that are more difficult to dissolve, requiring more energy to metabolise.

Furthermore, because the binding between silicon and oxygen is significantly stronger than the bond between carbon and oxygen, ${\mathrm{SiO}}_2$(silicon dioxide) is a solid, whereas ${\mathrm{CO}}_2$(carbon dioxide) is a gas. One of the advantages of carbon over silicon is that ${\mathrm{CO}}_2$can transport carbon more easily in the carbon cycle.

Therefore, carbon can form bonds easily and can participate in carbon cycling.