This chemical compound can dissolve in water to form hydroastatic acid, which exhibits properties very similar to the other five binary acids, and is in fact the strongest among them.

Because the atoms have a nearly equal electronegativity, and as the At+ ion has been observed,[6] dissociation could easily result in the hydrogen carrying the negative charge.

Furthermore, a trend for hydrogen halides, or HX, is that enthalpy of formation becomes less negative, i.e., decreases in magnitude but increases in absolute terms, as the halide becomes larger.

Finally, radiolysis from astatine nuclei could sever the H–At bonds.

The most stable is astatine-210, which has a half-life of approximately 8.1 hours, making its chemical compounds especially difficult to work with,[7] as the astatine will quickly decay into other elements.