Periodic table element types. The periodic table has 118 known elements (chemical symbols) arranged by increasing atomic number to form 18 groups (vertical columns) and 7 periods (horizontal rows). Included is each element's simple electron configuration,with electrons (red) filling successive shells around the nucleus. The elements are also colour-coded by type and properties: alkali metals (blue),alkaline earth metals (light blue),lanthanides (green),actinides (light green),transition metals (yellow),other metals (lilac),metalloids (light brown),halogens (orange),noble gases (pink),other non-metals (grey),and elements with unknown properties (white) |