This key facts covers From Mendeleev to the Modern Table within Development of Periodic Table for GCSE Chemistry. Revise Development of Periodic Table in Atomic Structure for GCSE Chemistry with 20 exam-style questions and 21 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 6 of 13 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.
🔄 From Mendeleev to the Modern Table
What changed?
- 1913 — Henry Moseley discovered elements should be arranged by atomic number (protons), not atomic weight
- This fixed the few elements Mendeleev had to swap around
- 1890s — Noble gases discovered and added as Group 0
Why atomic number works better: Atomic number = electrons = chemical properties!
Quick Check: Give two ways in which Mendeleev's periodic table was better than Newlands' table of octaves.
1. Mendeleev left gaps for undiscovered elements, whereas Newlands forced all known elements in without gaps. 2. Mendeleev predicted properties of the missing elements (confirmed when discovered), whereas Newlands made no predictions.
Practice questions for Development of Periodic Table
John Newlands proposed the Law of Octaves in 1866. What did he notice about the elements?
Give two reasons why Newlands' Law of Octaves was not accepted by the scientific community at the time.