Valency of Group 1 elements. Animation of the periodic table, showing the valency of the Group 1 elements, the alkali metals. The animation starts by showing the whole periodic table, followed by just the Group 1 elements (blue). The animation then shows the electron configuration of the first three elements in the group: lithium (Li), sodium (Na), and potassium (K). These elements have a single electron in their outermost electron shell. This is highlighted in red in both the electron shell diagrams and the numerical electron configuration below. The stability of an element's outer (valence) electrons determines its chemical and physical properties. For the groups shown here, the number of electrons in an element's outer electron shell corresponds to its group number in the periodic table. Group 1 is also known as group IA.