1. Unit 4: The Periodic Table How is the periodic table a useful tool?

2. Johann Döbereiner- 1817
Arranged elements into groups of three (triads) 1

4. John Newlands- 1864 The “Law of Octaves”
When arranged in order of increasing atomic weight, an element showed properties similar to those of an element 8 places ahead and 8 places behind
No noble gases discovered yet!

5. Dmitri Mendeleev- 1869 1

6. Dmitri Mendeleev- 1869 Published a table of 63 elements
Used properties to sort elements into groups
Arranged the elements in order of increasing atomic mass
Left blanks in table for undiscovered elements 1

7. Henry Moseley- 1913
Arranged elements according to atomic number (modern periodic table) 1