1. Learning Target Analyze and explain Rutherford’s Gold Foil Experiment.

2. Comparison of Atomic Models Dalton’s Model Thomson’s Model Rutherford’s Model

3. J.J. Thomson (IN 1896) A= Cathode B= Anode C= electrical source D= Positively charged plate E= negatively charged plate

4. http://highered.mcgraw- hill.com/sites/0072512644/student_view0/chapte r2/animations_center.html#http://highered.mcgraw- hill.com/sites/0072512644/student_view0/chapte r2/animations_center.html#

5. Robert Millikan - 1909 He measured the charge of an electron. Using this he gave a negative charge to oil droplets and was able to measure how different charged plates changed the droplets rate of fall. This also allowed him to measure the mass from the charge to mass ratio. http://highered.mcgraw- hill.com/sites/0072512644/student_view0/chapte r2/animations_center.html#

6. New Zealand Scientist Ernest Rutherford(1871- 1937) Had performed experiments to find that atoms were made of positively charged particles moving around a very tiny positively charged nucleus.

7. Rutherford’s Gold Foil experiment He did an famous experiment whereby he shot a stream of alpha particles at a thin piece of gold (Au) foil expecting most of the particles to be deflected-instead most of them passed directly through the foil and onto the photographic film

8. Rutherford experiment animation http://www.mhhe.com/physsci/che mistry/essentialchemistry/flash/rut her14.swf Rutherford’s Atomic Structure Model + =positively charged particles - = electrons

9. YOU WILL NEED: –NOTEBOOK –PERIODIC TABLE

11. Protons (positive) are bigger than electrons. The part of an atom that gives an element its identity. Neutrons (neutral) are slightly bigger in mass than a proton. Electrons (negative) charge, have a mass of close to zero-negligible

12. Atomic Mass Units (amu): roughly equal to the mass of a proton or neutron. **the mass of an atom is measured in amu’s 1 amu = 1.66x10 -24 g

13. ParticleLocation Charge(C)Mass (g)Mass (amu) ProtonInside nucleus 1.602 x 10 -19 1.673x10 -24 1.0073 =1 Neutron Inside nucleus 01.675x10 -24 1.0087 =1 Electron Outside nucleus -1.602 x 10 -14 7.109x10 -28 0.0006 =0

14. Every element has a unique atomic number which is the number of protons in the atom. Elements atomic number is just above the chemical symbol on periodic table. Atoms are electrically neutral-means number of protons always equal number of electrons.

15. Electron Number An Element’s atomic number also indicates number of electron in its atoms.

16. Ions Ions are atoms that have lost or gained one or more electrons giving them a positive or negative charge!

17. For example: Na (Sodium), has originally 11 electrons but when an electron is lost it becomes a positive ion. Na + If an ion loses an electron it has a positive charge. If an ion gains an electron it has a negative charge.

18. A neutral magnesium atom (atomic number=12) has 12 protons/electrons. If it loses 2 electrons it becomes an ion with a charge of 2+. Number of protons 12 Number of electrons - 10 Charge of Ion 2+

19. 19. Cu² + 20. As 3- 29 33 Ion Protons Electrons 27 36

20. Isotopes Isotopes are atoms that have the same number of protons but different numbers of neutrons Most elements in the first two rows of the periodic table have at least 2 isotopes with one being more common than the other In nature, elements are almost always found as a mixture of isotopes

21. Differences between isotopes? Isotopes react in the same way as others of the same element

22. Atomic mass Atomic Number/ number of protons Atomic mass: weighted average of the masses of the existing isotopes of an element.

23. What was Dalton’s 2 nd Postulate? Was it correct? Hmmm

24. The most common isotope of hydrogen has no neutrons at all There's also a hydrogen isotope called deuterium, with one neutron, and another, tritium, with two neutrons. Isotopes of Hydrogen

25. To identify an isotope more specifically, chemists add a number after the elements name. ex. Carbon-11 Carbon-12 Carbon-14 This number is called the isotope’s mass number and is the sum of the isotope’s number of protons and neutrons. What is the atomic mass on your Periodic Table? Which of the 3 isotopes of Carbon is the most abundant?

26. Complete Chemical Symbols 141 56 Mass number Atomic number Charge Ba 2+ Number of protons = Atomic # Number of neutrons = Mass # - Atomic # Charge = Atomic # – Number of electrons

27. Complete the Table Chemical Symbol No. of Protons No. of Electrons No. of Neutrons Atom or Ion? 38 Sr 2+ 464550 1429Atom 90

28. WARM UP What is the atomic mass unit of a proton? Neutron? Electron? What is the atomic mass of an element represent?

29. Complete the Table Chemical Symbol No. of Protons No. of Electrons No. of Neutrons Atom or Ion? 38 Sr 2+ 464550 1429Atom 90