1.  Introduction to Chemistry Chemistry 20

2. Before we begin…

3. Agenda  Start new unit  Activity  History of Elements

4. Activity

5. Ancient Greece  (445 BC) Empedocles claims there are four elements: Earth, Air, Fire and Water

7. Democritus Proposed that matter was made out of extremely small particles called atoms. These atoms were named after the Greek word ‘atomos’, which means indivisible.

8. Democritus  He also proposed how the atoms were shaped as well as how they connected.  He reasoned that the solidness of the material corresponded to the shape of the atoms involved.

9. Iron atoms are solid and strong with hooks that lock them into a solid. Water atoms are smooth and slippery. Salt atoms are sharp and pointed due to their taste. Air atoms are light and swirling, pervading all other materials

10. Aristotle

11.  Came up with the idea that matter varied with different balances of temperature and humidity. (Cold, Hot, Wet and Dry)  This idea because very popular, and somewhat held back how people thought about atoms and elements.  Because of the idea that the difference between different materials was only a matter of balance, it spawned a huge amount of scientists that would try and change one metal into another.

12. Alchemy

13.  Most intellectual people of their time  Sought after the Philosopher’s Stone, which would allow them to turn cheap metals like copper into valuable ones like gold.  Alchemists also sought immortality. They wanted to create something known as the ‘Elixer of Life’, which would grant this.  Was practiced across most of Europe by the 13 th century.

14. Robert Boyle Often regarded as the first modern chemist. Although an alchemist, was very adamant that chemistry was the study of composition, and not just a branch of alchemy.

15. Robert Boyle In 1661, he published his first book titled, “The Sceptical Chymist” Suggested that matter wasn’t made of Earth, Air, Fire, and Water, but rather other materials.

16. Antoine Lavoisier Lived in France from 1743- 1794 Metric System Conservation of Mass “Methode de Nomenclature Chimique”

17. Antoine Lavoisier Killed in the French Revolution Named Oxygen and Hydrogen

18.  But what do atoms look like?

19. John Dalton Proposed his Atomic Theory in 1803 His data came from experimentation

20. Dalton’s Atomic Theory  Elements are made of extremely small particles called atoms.  Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties.  Atoms cannot be subdivided, created, or destroyed.  Atoms of different elements combine in simple whole-number ratios to form chemical compounds.  In chemical reactions, atoms are combined, separated, or rearranged.

21. But what did these atoms look like? DemocritusJohn Dalton

22. J. J. Thomson Discovered the electron. Also discovered isotopes The discovery of the electron changed what the atom looked like.

23. “Plum-Pudding Model” If it is easier to remember, it is kind of like cookie dough.

24. Ernest Rutherford Conducted the “gold-foil experiment”. Discovered the presence of a nucleus. In later work, discovered that the nucleus was positively charged.

26. Rutherford Model of Atom

27. Niels Bohr Said electrons orbit the nucleus in a certain fashion. James Chadwick discovered the neutron in 1932, shown by the orange dots in the image.

28. Current Information NameSymbolLocationRelative Charge Relative Mass Protonp+p+ In Nucleus1+1 Neutronn0n0 In Nucleus01 Electrone-e- Orbitals1-1/1840

29.  Other Important Scientists

30. Lorenzo Romano Amedeo Carlo Avagadro Discovered that two equal volumes of gases, contain the same number of molecules This allows us to measure the size and weight of atoms!

32. Dmitri Mendeleev Made the periodic table. Listed elements on the table by mass Predicted the discovery of new elements. Predicted the properties those elements would have.

33.  Activity!