1. The Periodic Table

2. Why is it put together the way it is?
Logical grouping, not just thrown together
Why not a better shape, something that is… a 10 x 10 element square – that would look better…
It is in order by….
Increasing number of protons

3. Who put it all together?
Dmitri Mendeleev
In the mid 1800s

4. Mendeleev At his time, there were 63 known elements
He used the physical/chemical properties and noticed patterns
He made up a “card” for each element and wrote the chemical and physical properties of that element on the card
He then arranged them by atomic mass. He noticed that similar properties occurred every 8 elements

5. Mendeleev’s Periodic Table
Mendeleev even left spaces for elements that had not been discovered, and he predicted their properties

6. Valence Electrons
How many valence electrons does H have?
Li?
Na? K?

7. Be?
Mg?

8. B?
Al? C?
Si?

9. He?
Ne?
Ar?

10. The number of valence electrons predicts the properties of the elements!

11. Henry Moseley 50 years after Mendeleev
Determined the atomic number of all elements and found that elements should be arranged by atomic number rather than atomic mass
Developed periodic law
Physical and chemical properties of the elements are periodic functions of their atomic numbers