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Write the names and formulas of the oxides and oxygen acids of selenium and tellurium.

It is a black solid melting at 570 degrees; it is a metallic looking element, will conduct electricity somewhat, oxidizes in air to form an acidic oxide, and forms strong oxygen acids.

It is dissolved by the oxygen acids with the disengagement of oxygen gas.

In later years Berzelius renounced the ``oxygen acid'' theory, but not before Davy, and, almost simultaneously, Dulong, had submitted that hydrogen and not oxygen was the acidifying principle.

They also form oxides and oxygen acids which resemble the corresponding sulphur compounds.