2. chlorine, a poisonous greenish gas, has an irritating odor
3. bromine, a toxic and caustic red-brown volatile liquid at room temperature
4. iodine, a shiny dark grey crystalline solid at room temperature but which
easily sublimes to form a violet vapour on heating
N.B. All the isotopes of astatine are radioactive, and so this element will not be
considered any further here.
African Virtual University
Chemical Properties
1. All halogens have seven valence electrons which form ions with a negative
(-1) charge
2. Fluorine is the most reactive of all the nonmetals