I’m sorry but it seems you have requested information about a unclear or non-existent chemical substance. B2Se5Te2 is not a valid chemical formula in the periodic table.
When we talk about chemistry, we usually refer to the chemical elements and the chemical compounds they form. B2Se5Te2 could be understood as a chemical compound containing the elements Boron (B), Selenium (Se), and Tellurium (Te). However, this formula cannot exist in reality as these elements cannot combine in this ratio to form a stable compound.
In this case, I advise you to verify the information about the chemical substance you want to explore. The Mendeleyev Periodic Table provides clear information about the 118 known chemical elements and the compounds they can form.