Unfortunately, there seems to be no information about the compound Se5O5 in the context of chemistry. It appears to be a mistake in the chemical notation. Selenium (Se) and Oxygen (O) can bond to form various compounds, but Se5O5 is not one of them.
Therefore, it’s difficult to provide information about its name, atomic mass, molar mass, ion structure, physical and chemical properties, such as color, smell, pH level, reactions with metals, acids, non-metals, salts, and specific synthesis methods.
However, if you wish to know about a particular compound between Selenium and Oxygen, I would be more than happy to assist. An example of a Selenium and Oxygen compound is Selenium dioxide (SeO2), a white solid used as a bleach, oxidizer and reagent in the chemical industry.
I hope this helps, and I apologize for any misunderstanding.