# What's the relation between electronic configuration and chemical reactivity?

${s}^{2} {p}^{6}$ is the stable electron configuration of the noble gases. Group VIII A The electron orbitals are completely filled. this is a very stable electron configuration so the noble gases are very unreactive.
${s}^{2} {p}^{5}$ is the unstable electron configuration of the Halides Group VII A. The p orbitals are short one electron and not quite completely filled. This is a very unstable electron configuration. The atom will attempt to gain an electron to fill the orbitals. This makes the Halides the most reactive of the non metals.