The periodic table traditionally taught in textbooks, which organizes elements based on chemical traits such as reactivity ... to nonmetals and other chemical trends across elements.

The group 1 elements are all soft, reactive metals with low melting points. They react with water to produce an alkaline metal hydroxide solution and hydrogen. Reactivity increases down the group.

The noble gases are a group of chemical elements with very low reactivity ... be an unrecognised new element in the air. The periodic table devised by Dmitri Mendeleev in 1869 had only seven ...