1. Basics Of Chemistry 8 th Science 2012

2. Matter Defined ► Matter – anything that has volume or mass. ► Everything you see and don’t see.

3. Definitions ► Element- pure substance that cannot be separated into simpler substances by physical or chemical means.  Represented by a symbol – Au stands for what?

4. Definitions ► Atom – Smallest particle into which an element can be divided and still be the same substance, retaining its properties

5. Evolution of the Atomic Theory ► Democritis – 440 BC ► Greek philosopher who said that if you cut a substance in half again and again and again eventually you would have an “uncuttable” piece ► said that all atoms made of a single material formed into different shapes and they join together to make different materials ► Greek word atomos, which means “indivisible”

6. John Dalton - 1803 ► Studied the atmosphere and other gases and developed atomic theory. ► Dalton demonstrated that elements combine in specific proportions to make different substances

7. John Dalton’s Atomic Theory ► 1. All substances are made of atoms. ► 2. Atoms are small particles that cannot be created, divided, or destroyed. Dalton’s New System of Chemical Philosophy

8. Dalton’s Atomic Theory, continued ► 3. Atoms of the same element are identical in size, mass and other properties. ► 4. Atoms of different elements combine to make chemical compounds. ► 5. In chemical reactions, atoms are combined, separated, or rearranged. chemical reactionschemical reactions

9. J.J. Thomson - 1897 ► discovered that there are small particles inside the atom, so the atom can be divided into smaller parts

10. JJ Thomson, continued ► Experimented, using a cathode-ray tube to discover negative particles he called corpuscles ► these negatively charged particles found in all atoms are now called electrons

11. Thomson’s Model ► Plum Pudding model ► Described electrons as scattered all about the atom

12. Ernest Rutherford - 1908

13. Rutherford, continued ► Discovered a tiny, extremely dense, positively charged region called a nucleus ► Most of the atom’s mass was in the nucleus and electrons traveled around the nucleus

14. Rutherford cont’d ► said the atom was mostly empty space

15. Niels Bohr – 1913 ► said the electrons travel around the nucleus in definite paths

16. Erwin Schrödinger and Werner Heisenberg - 1926 ► Said electrons travel in clouds, not definite paths but we still use the Bohr Model to represent atoms.

17. The Atom

18. Subatomic Particles Protons Determine the identity of the matter ► positively charged particles ► found in the nucleus ► ► Mass =1.67262158 × 10 -27 kilograms 0.000000000000000000000000017 kg ► Each proton is 1 amu  AMU stands for Atomic Mass Unit

19. Subatomic Particles Neutrons Neutrons are the glue that holds the protons together in the nucleus ► no charge ► found in the nucleus ► mass is 1 amu

20. Subatomic Particles Electrons Determine the reactivity ► Negatively charged ► Found around the nucleus within electron clouds ► Mass is very small, almost zero

21. Atoms are NEUTRAL ► Atoms are neutral because the number of protons equals the number of electrons.

22. How To Read a Square ► 8 ► O ► Oxygen ► 15.9994 ► Elements are identified by their atomic number – the number of protons. Also equals the number of electrons. ► Chemical Symbol ► Element Name ► Atomic Mass

23. PEN Method ► SLIDE, SLIDE, ROUND THE BOTTOM SUBTRACT TOP ► P = 8 ► E = 8 ► N = 8 ► 8 ► O ► Oxygen ► 15.9994