1. Organizing the Elements

2. The Beginning
Before written history, people were aware of some of the elements in the periodic table. Elements such as gold (Au), silver (Ag), copper (Cu), lead (Pb), tin (Sn), and mercury (Hg).
It wasn't until 1649, however, until the first element was discovered through scientific inquiry by Hennig Brand . That element was phosphorous (P).

3. 1800s
Electricity – used to break down compounds into element components
Spectometer – used to identify the isolated elements
Industrial revolution – making soaps, dyes, fertilizers
By 1869, 63 elements had been discovered.

4. Putting it together…

5. John Newlands (1864) Arranged elements by increasing atomic mass
English chemist

6. John Newlands (1864)
Created the law of octaves (properties repeat every 8th element)
Didn’t work for every element and music analogy wasn’t scientific

7. Meyer and Mendeleev (1869) Arranged elements by increasing atomic mass
Russian chemist
German chemist
Mendeleev published his findings first so he usually gets more credit

8. Meyer and Mendeleev (1869)
noted a connection between atomic mass and properties
Arranged elements with similar properties horizontally

9. Meyer and Mendeleev (1869)
Predicted existence and properties of unknown elements
eka-aluminum, eka-boron,
and eka-silicon. The elements gallium, scandium and germanium were found later to fit his predictions quite well.

10. Problems
Mendeleev’s table wasn’t completely correct – As new elements were discovered, arranging the elements by atomic mass put some elements with groups that had different properties
The atomic weight of the gas argon, which does not react readily with other elements, would place it in the same group as the chemically very active solids lithium and sodium.

11. Moseley (1913) Arranged elements by increasing atomic number
Number of electrons in the atom
(or the number of protons in the nucleus)

12. Moseley (1913)
Discovered a clear periodic pattern of properties

13. The Periodic Table of Elements – a chart that organizes the elements

14. The Modern Periodic Table
Made of boxes and arranged by atomic number

15. Modern Periodic Table

16. Groups
Vertical columns (families)

17. Groups
Elements in same group have very similar properties

18. Periods
Horizontal rows

19. Periods
Patterns of similar properties repeat with each period