Development of the Modern Periodic Table

1. Development of the Modern Periodic Table Chapter 6 Section 1

2. History • Late 1790s, French scientist Antoine Lavoisier compiled list of elements. • 23 elements at the time milenao.blogs.sapo.pt

3. History (cont.) • During 1800s, electricity, development of a spectrometer and the industrial revolution helped to discover new elements. • 1860 – They agreed on a method to determine atomic masses. • Chemists needed a tool to organize facts about elements. • 1870 – 70 elements

4. John Newlands • In 1864, John Newlands, an English chemist proposed an organization scheme for elements. • Observed a pattern that was periodic. • Called the Law of Octaves because the pattern repeated every 8th element. www.neoam.cc.ok.us

5. John Newlands (cont.) • Harshly criticized for using musical analogy • Law did not work for every element • Elements were arranged by atomic mass

6. Meyer, Mendeleev and Moseley • In 1869, Lothar Meyer, a German chemist and Dmitri Mendeleev, a Russian chemist showed a connection between atomic mass and elemental properties www.apsidium.com www.bluffton.edu

7. Meyer, Mendeleev and Moseley • Mendeleev published first so he’s given more credit than Meyer and he better demonstrated its usefulness. • Arranged by increasing atomic mass had periodic properties. • Table had blank spaces for undiscovered elements.

8. Meyer, Mendeleev and Moseley • Mendeleev’s table was not completely accurate. • In 1913, Henry Moseley, an English chemist arranged atoms by increasing atomic number. • This arrangement showed a clear periodic pattern of properties (periodic law).