What is the smallest atom having tetra-valency?

Answer 1

Carbon is the smallest atom having tetravalency. Note that carbon is the atom in the uppermost* period of a wide form Periodic Table that includes column 14, the column in which the most common valency is tetravalency, and in general atomic size is greater the lower in a periodic table that the atom appears.

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*This is the second period of the table as a whole; the first period includes only columns 1 and 18.

Answer 2

Carbon is the smallest atom that exhibits tetra-valency, meaning it can form four bonds with other atoms. This property is due to its atomic structure that includes four valence electrons available for bonding.