Block (periodic table) form compounds. The first period elements in this block, however, are nonmetals. Hydrogen is highly chemically reactive, like the other s-block elements, but helium is a virtually unreactive noble gas. S-block elements are unified by the fact that their valence electrons (outermost electrons) are in the s orbital. The s-orbital is a single spherical cloud which can contain only one pair of electrons; hence, the s-block consists of only two columns in the periodic table. Elements in column 1, with a single s-orbital valence electron, are the most reactive of the block. Elements in the second column have two s-orbital
Extended periodic table (detailed cells) Extended periodic table (detailed cells) This is a large version of the extended periodic table of the chemical elements. For the natural isotopic composition of each element it shows "name", "atomic number", "symbol", "standard atomic weight" (or atomic weight) and a link to the element's isotopes. It also has, by keyed markings, a notification of "occurrence", "state of matter" and "metallic character". It is named "extended" because it shows elements that are theoretical only (in period 8), and "large" means that the table might exceed page width. The presentation is wide which means that there are no table parts separated