Editing Period 6 element (section)

{{Short description|Row 6 of the periodic table}}
{{Periodic table (micro)| title=Period 6 in the [[periodic table]] | mark=Cs,Ba,La,Ce,Pr,Nd,Pm,Sm,Eu,Gd,Tb,Dy,Ho,Er,Tm,Yb,Lu,Hf,Ta,W,Re,Os,Ir,Pt,Au,Hg,Tl,Pb,Bi,Po,At,Rn}}
{{Sidebar periodic table|expanded=structure }}
A '''period 6 element''' is one of the [[chemical element]]s in the sixth row (or [[Periodic table period|period]]) of the [[periodic table|periodic table of the chemical elements]], including the [[lanthanide]]s. The periodic table is laid out in rows to illustrate recurring (periodic) trends in the chemical behaviour of the elements as their atomic number increases: a new row is begun when chemical behaviour begins to repeat, meaning that elements with similar behaviour fall into the same vertical columns. The sixth period contains 32 elements, tied for the most with [[Period 7 element|period 7]], beginning with [[caesium]] and ending with [[radon]]. [[Lead]] is currently the last stable element; all subsequent elements are [[radioactive]]. For [[bismuth]], however, its only [[primordial isotope]], <sup>209</sup>Bi, has a half-life of more than 10<sup>19</sup> years, over a billion times longer than the current [[age of the universe]]. As a rule, period 6 elements fill their 6s [[electron shell|shells]] first, then their 4f, 5d, and 6p shells, in that order; however, there are exceptions, such as [[gold]].