a physical property is that it's odorous. which is why one of his superpowers is that he lets out a deadly, odorous gas.
a physical property is that bromine is irritating to the skin and can literally dissolve the human skin, which is why he has eyes the shoot the bromine at his desired length and amount.
a weakness for broboy is that he melts easy. he melts at 19.04 degrees Fahrenheit. therefore he will die when exposed to regular weather. but that's only when he doesn't have on his cloak, which keeps him at least -5 below.