Mendeleev discovered the periodic table (or Periodic System, as he called it ... but Mendeleev saw that iodine was very similar to the rest of the halogens (fluorine, chlorine, bromine), and tellurium ...

When the alkali metals react with the different halogens (Group 7 of the periodic table), the group of compounds formed are known as the alkali metals halides. Due to the fact that there are a ...

The zigzag, staircase, line in the diagram of the periodic table above separates the metals, on the left, from non-metals, on the right. Hydrogen is a non-metal, but it is often put in the middle.