States and Colors, at RTP: Fluorine- Yellow gas Chlorine- Green gas Bromine- Red liquid Iodine- Black solid | Down the group; size, mass and density increase |
Diatomic; form halide ions in displacement reaction | Reactivity decreases down the group, because it has to gain an electron, so the closer the electron is to the positive nucleus the more easily it will be gained, so atoms with fewer shells will react more easily. |