1. Matter & The Atom

2. Matter The term matter describes all of the physical substances around us: your table, your body, a pencil, water, and so forth

3. Matter Anything that has mass and takes up space (has volume) Made up of different kinds of atoms

4. Matter Includes all things that can be seen, tasted, smelled, or touched Does not include heat, sound, or light

5. Matter is made of atoms

6. Models Models are often used for things that are too small or too large to be observed or that are too difficult to be understood easily

7. Models In the case of atoms, scientists use large models to explain something that is very small Models of the atom were used to explain data or facts that were gathered experimentally. So, these models are also theories

8. Early Models of the Atom Democritus Universe was made of empty space and tiny bits of stuff Called these tiny bits of stuff atomos Atoms could not be divided

9. Early Models of the Atom Lavoisier Demonstrated that burning wood caused no change in mass Law of Conservation of Matter

10. Early Models of the Atom Dalton All elements are composed of indivisible particles. Atoms of the same element are the same Atoms of different elements are different. Compounds consisted of atoms of different elements combined together

11. Early Models of the Atom Thomson Plum pudding model Atom made of a positively charged material with the negatively charged electrons scattered through it.

12. Early Models of the Atom Rutherford Mostly empty space Small, positive nucleus Contained protons Negative electrons scattered around the outside

13. Early Models of the Atom Bohr Electrons move in definite orbits around the nucleus

14. Early Models of the Atom Chadwick Discovered the neutron

15. Modern Model of the Atom The electron cloud Sometimes called the wave model Spherical cloud of varying density Varying density shows where an electron is more or less likely to be

16. Atomic Structure Nucleus –Protons –Neutrons Electrons

17. Atomic Structure Electrons Tiny, very light particles Have a negative electrical charge (-) Move around the outside of the nucleus

18. Atomic Structure Protons Much larger and heavier than electrons Protons have a positive charge (+) Located in the nucleus of the atom

19. Atomic Structure Neutrons Large and heavy like protons Neutrons have no electrical charge Located in the nucleus of the atom

20. Atomic Structure

21. Describing Atoms Atomic Number = number of protons In a neutral atom, the # of protons = the # of electrons

22. Describing Atoms Atomic Mass Number - equal to the number of protons plus neutrons.