the iron molecules would rather react with Bromine instead of Iodine. So, the iron molecules switch over to bromine leaving the iodine molecules by themselves.
In HCl ,bond between hydrogen and chlorine is covalent. But due to difference in electronegativity of hydrogen and chlorine,shared electron pair gets attracted towards chlorine. Due to this polar covalent
since there are three phosphorus use the prefix tri-, since there are five nitrogen use the prefix penta. tri=3, penta=5. then add a suffix -ide to the end of nitrogen. that will give you triphosphorus pentanitride.