Question

When you look at the periodic table (chemistry), there are a few patterns. One of which is that elements in the same column have the same electron arrangement in their outermost electron shell.

A common theme in science fiction is lifeforms based on silicon rather than carbon. Why would silicon be a better substitute for carbon than something like boron or nitrogen? You may need to look at a periodic table of elements for this question. Boron is element number 5, carbon number 6, nitrogen number 7, and silicon is element number 14.

Answer 1

Carbon is abundantly present in all the biomolecules because of its two properties, tetravalency and catenation.

By term tetravalency, I mean to say that the carbon 4 electrons in its outermost orbit. Therefore it is able to form 4 bonds with other atoms.

By the term catenation, I mean to say that carbon is able to associate with itself and form long Chains of carbon atom.

Silicon is another molecule which would have been present in living organisms if carbon would be there. This is because silicon is also tetravalent like carbon and is able to form 4 bonds with the large number of atoms.

But the property of catenation is not seen in Silicon and that is why it is not actually present in Living Organisms.

Other elements like Boron and nitrogen are not that abundantly present in living cells because they are not tetravalent in nature. They cannot form covalent bond with large number of atoms. All the nitrogen is trivalent and can form covalent bonds with three atoms at a time, but still it is not equivalent to a tetravalent atom like carbon.

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