Valency and the periodic table. Animation of the periodic table, showing the valency of the Group 1 elements (the alkali metals) and the Group 17 elements (the halogens). The animation starts by showing the whole periodic table, followed by highlighting the Group 1 elements (blue, highlighted in red), and shows the electron configuration of the first element in the group: lithium (Li). This element, like others in the group, has a single electron in its outermost electron shell. This is highlighted in red in the electron shell diagram. The animation then highlights the Group 17 elements (red, highlighted in red), and shows the electron configuration of the first element in the group: fluorine (F). This element, like others in the group, has seven electrons in its outermost electron shell. This is highlighted in red in the electron shell diagram. 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. Groups 1 is also known as group IA. Group 17 is also known as group VIIA and group 7. |