1. 9/29 – Warm Up #2 What are the subatomic particles found in the nucleus? With this information, predict the charge of the nucleus. The mass of silver in a beaker is 35.0 grams. When the silver is dropped into the beaker, the volume of the water changes. If the water level was initially at 25.0 mL, calculate the final volume of water, in mL. Fill in the blanks: “Opposites ______ (attract/repel), while like charges _______ (attract/repel).”

2. 9/30 – Warm Up #3 In the early 1900’s, Ernest Rutherford performed an experiment where he shot a POSITIVELY-CHARGED beam of radiation at a piece of gold foil. First of all, remember that opposite charges ______ and like charges _____. Most of the time, the beam of radiation went THROUGH the foil. This means most of the foil had a ________ charge. What part of the atom is this? On rare occasions, the beam of radiation got DEFLECTED when it hit the foil. This means some of the foil had a _____ charge. What part of the atom is this?

3. The Nucleus, Atomic Mass and Isotopes

4. Remember: Nucleus = protons and neutrons (POSITIVELY CHARGED) DENSE – a lot of matter in a small space A VERY small portion of the atom (mostly empty space)

5. Also Keep in Mind… Charges = positive, negative, neutral Like charges REPEL Positive repels Positive Negative repels Negative Opposite charges ATTRACT Positive attracts Negative Negative attracts Positive

6. Ernest Rutherford (1871-1937) Discovered nucleus Before him: atoms = positively charged blobs with some negative charged particles in it Experiment: shot laser w/positive charged particles into gold foil

7. What Rutherford Found… Most particles go through gold foil BUT Some particles deflected MEANING Most of gold foil = negative- charged (electrons) Small positive charged center (NUCLEUS)

8. Nucleus Continued On Periodic Table: Atomic Number – Number of PROTONS an atom has STAYS CONSTANT (ALWAYS) Element Symbol

9. Isotopes! Isotopes – The same element, but different numbers of neutrons Different FORMS of the element Carbon 12 (mass # = 12) Ex. Carbon Carbon-12 (6p, 6n) Carbon-13 (6p, 7n) Carbon-14 (6p, 8n) (radioactive)

10. To Find Atomic Mass… Take ALL forms of element in universe, and find AVERAGE Ex. Carbon Atomic Mass: 12.01 grams A LOT of carbon-12 Small amount of carbon-13 and 14 Carbon-12 Shorthand Notation C 12 6 Mass # - # of protons + neutrons Atomic# - # of protons

11. Nucleus Continued On Periodic Table: Average Mass – avg. mass of all isotopes of the atom In grams Also called MOLAR MASS

12. Protons and Neutrons Protons do not always equal neutrons Ex. Aluminum Atomic # 13 (13 protons) Mass: 26.98g (13 protons + 14 neutrons) Why does this occur? Aluminum

13. Warm Up #4 For an element, which number will stay the same and which number can be different? (atomic number or mass number). Explain why. Why is the bottom number on the periodic table the AVERAGE atomic mass? Use “isotope” in your answer. Write the correct short-hand notation of Carbon-13 (include mass number and atomic number) If an element has an atomic number of 30, and a mass number of 65, how many neutrons does it have?