The finished puzzle is a section of the periodic table, so the numbers on each tile are their atomic numbers - that means they increase from left to right and top to bottom. Another helpful clue ...

It wasn’t until 1913, six years after Mendeleev’s death that the final piece of the puzzle fell into place. The periodic table was arranged by atomic mass, and this nearly always gives the same order ...

Want to learn more about this centerpiece of chemistry? Take your pick from this collection of links about elements and the periodic table! Build an element ball, solve periodic puzzles, and check out ...

From the smallest trace elements to the largest building blocks, each piece of the puzzle is vital for creating and sustaining human life. So the next time you look at the periodic table ...