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Why can orthotelluric acid, Te(OH)6, exist while S(OH)6 does not?

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A color-coded periodic table of the elements displays each element's symbol and atomic number, with categories such as alkali metals, noble gases, halogens, transition metals, and actinoid elements distinguished by different background colors. — oxygen group element Modern version of the periodic table of the elements (printable).

The existence of orthotelluric acid, ${Te(OH)}_{6}$ , compared to the nonexistence of ${S(OH)}_{6}$ , is primarily explained by the periodic trends in atomic size and charge density within the oxygen group.1

While sulfur is capable of forming stable compounds in the +6 oxidation state, such as ${SF}_{6}$ , the hypothetical ${S(OH)}_{6}$ molecule does not exist due to the high charge density of the sulfur atom in that state. The small diameter of the sulfur atom relative to its positive charge creates significant electrostatic repulsion toward the electropositive hydrogen atoms in the hydroxyl groups. Furthermore, the physical crowding that occurs when six oxygen atoms are covalently bonded to a relatively small sulfur atom destabilizes the structure, favoring the loss of water.1

As one moves down the group to tellurium, the atomic size increases significantly. This larger atomic radius reduces the charge density and alleviates the steric crowding associated with bonding six oxygen atoms, allowing orthotelluric acid to exist as a stable compound.12