The Evolution of the Periodic Table

The periodic table is literally organized backwards from what you'd expect. When Mendeleev first

published it in 1869, he arranged elements by atomic mass, but something was

off. Elements like iodine and tellurium were in the wrong spots. Then in 1911,

Henry Moseley discovered the game changer: organizing by number of protons instead of mass fixed everything.

This became the Periodic Law. But here's the wild part: as you move left to right across

the table, atoms actually get smaller even though they have more protons. Why?

Because those extra protons pull electrons tighter to the nucleus. Meanwhile, going down adds

whole new energy levels, making atoms bigger. The entire chemistry of our universe