With less electronegative elements they form halide compounds, and this is the only group which has members existing in solid, liquid, and gaseous states at room conditions.
The addition reaction of these elements occurs when one of these elements is added to the carbon double bond of an alkene functional group. These elements act as electrophilic species in their namesake bonds, which are used in crystal engineering, and the pseudo form of these elements is often made of cyanides and cyanate ions bonded to members of this group. With less electronegative elements they form halide compounds, and this is the only group which has members existing in solid, liquid, and gaseous states at room conditions. For 10 points, name this group of elements with seven valence electrons, which includes bromine and iodine.
The addition reaction of these elements occurs when one of these elements is added to the carbon double bond of an alkene functional group.
Halogens [accept Group 17 or Group 7A]