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

2. History Late 1790s, French scientist Antoine Lavoisier compiled list of elements. Late 1790s, French scientist Antoine Lavoisier compiled list of elements. 23 elements at the time 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. 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. 1860 – They agreed on a method to determine atomic masses. Chemists needed a tool to organize facts about elements. Chemists needed a tool to organize facts about elements. 1870 – 70 elements 1870 – 70 elements

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

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

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

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