Periodic Table of Elements Timeline

The periodic table of elements is a tabular display of the chemical elements found on planet Earth.
The periodic table of elements is said to be invented by Dimitri Mendeleev, in 1869, and he arranged the chemical elements by atomic mass. In 1886 French physicist Antoine Bequeri first discovered radioactivity.

Who Invented the Periodic Table?

Dmitri Ivanovich Mendeleev — a Russian chemist — is the person credited with creating the first widely recognized periodic table, published in 1869. 

He is the father of the Periodic Table (1869). The modern version we use today is based on his design, later refined by atomic number instead of atomic mass.

He arranged elements by atomic weight and noticed their properties repeated in a pattern → the Periodic Law.

A German chemist named Lothar Meyer made a very similar table around the same time (published 1870, one year later). Others like John Newlands also contributed earlier, but Mendeleev gets the main credit because his table was published first, and it successfully predicted unknown elements.

In short: Mendeleev drew the map, Moseley fixed the numbering, Seaborg gave it the shape, and we finished the 7th row in 2016!

Would you like a simplified one-page version of the table itself?

PERIODIC TABLE TIMELINE

1869 — Mendeleev's First Table

• Dmitri Mendeleev (Russia) published the first table with 63 known elements, ordered by atomic weight.
• Genius: Left empty gaps for undiscovered elements and predicted their properties.
• Within 15 years — Gallium (1875), Scandium (1879), Germanium (1886) were found — matching his predictions almost perfectly!

1894–1900 — Noble Gases Added

• William Ramsay & Lord Rayleigh discovered Argon, then Helium, Neon, Krypton, Xenon.
• A whole new column (Group 18) was added — Mendeleev hadn't predicted these, but they fit perfectly.

1913 — Moseley Fixes the Rule (Big Change!)

• Henry Moseley used X-rays to prove elements should be ordered by ATOMIC NUMBER (protons), NOT atomic weight.
• This fixed all the earlier mismatches (e.g., Argon/Potassium, Tellurium/Iodine).
• → The Modern Periodic Law was born.

1940–1945 — Seaborg Shapes the Modern Look

• Glenn T. Seaborg discovered Plutonium and many transuranium elements.
• Proposed pulling out the Lanthanides & Actinides into their own separate rows at the bottom.
• This gave the table its current shape we see today.

2016 — The 7th Row is Complete!

• IUPAC officially recognized 4 new elements:
  • 113 Nihonium, 115 Moscovium, 117 Tennessine, 118 Oganesson
• All 7 periods filled — 118 confirmed elements total.

2021 → Today

• IUPAC published updated official guidelines for naming and structure.
• Search continues for elements 119+ (8th period — still theoretical).

Year	Who	What Changed
1869	Mendeleev	First table — by atomic mass, with gaps
1894	Ramsay	Noble gases added (new column)
1913	Moseley	Ordered by atomic number → modern law
1945	Seaborg	Lanthanides/Actinides at bottom → modern shape
2016	IUPAC	7th row complete → 118 elements