Reactive Elements that do not exhibit the characteristics of metals. These elements differ markedly from metals in respect to electronegativity and thermal and electrical conductivity. These elements, in general, are poor conductors and have high electronegativity. This series includes halogens, noblegases and some of the metalloids (B, Si, As and Te). Click on Term to Read More that is in Group 17 (VIIA) of the periodic table: F, Cl, Br, I and At. All of halogen elements are strongly electronegative.