Atom Structure: Electron Shells

Learn why electron shells are responsible for the properties of elements, and whether they are stable or have violent reactions. Chemistry - Atoms And Bonding - Learning Points. An element's reactivity is determined by the number of electrons in the outer shell of its atom. To be perfectly stable, an atom requires a full outer shell of electrons. The inner shell of every atom can hold only two electrons - as the shells move further away from the nucleus, they can accommodate more electrons. Potassium, with a single outer shell electron, will react with other elements to leave it with a full outer shell. A Twig Curriculum Film. Delivering key learning points. Get straight to the facts in just three minutes – directly linked to core learning, Twig's curriculum films will fit neatly into your lesson plans.