Question

Some scientists think that life elsewhere in the universe might be based on the element silicon, rather than carbon, as on Earth. Look at the electron distribution diagram for Silicon in Figure 2.7 and draw the Lewis dot structure for silicon. What properties does silicon share with carbon that would make silicon-based life more likely than, say, neon-based life or aluminum-based life?

Short answer

Silicon has the same number of valence electrons as carbon.So, like carbon, silicon can form long branched polymers and construct the skeleton of molecules. On the contrary, neon has no valence electrons, whereas aluminum has three valence electrons, making these elements less likely than silicon-based life.

Step-by-step solution

Human life is based on carbon

A carbon atom has four valence electrons, and therefore it can form four covalent bonds with other atoms. Thus, several carbon atoms can bond to each other and to other atoms to form long-chain molecules.

DNA and proteins are long-chain carbon molecules and form the basis of life. Thus, carbon forms the basis of life.

Lewis dot structure for silicon

Lewis dot structure refers to a simple representation of valence electrons of elements in a molecule. It does show the electrons present in the lower energy levels.

The valence electrons of the elements in this structure are shown as dots surrounding the symbol of the element. The Lewis dot structure of silicon would be Si surrounded by four dots as silicon has four valence shell electrons.

Similarity between Silicon and carbon

Both carbon and silicon belong to group IV of the periodic table. This means they both possess four electrons in their valence shell and thus share many properties.

Each of these elements can form four bonds with other elements. Both these elements can bond with oxygen. Each can form a long chain of branched polymers with oxygen present alternatively.

On the other hand, neon is an inert gas that cannot form stable substances and polymers, and aluminum with three electrons in its valence shell cannot form long-chain branched polymers like silicon that would form the skeleton of molecules.

Thus, silicon-based life can be expected as compared to neon or aluminum in other parts of the universe based on the similarities between silicon and carbon.