Name Class period Date Chapter 4: The Atom CHEM 6 know and understand the historical development of atomic theory. You can Describe the history of the atom and contributions of scientists: J. J. Thomson, John Dalton, Ernest Rutherford name and identify the subatomic particles of the nucleus of an atom. describe the properties of the subatomic particles of the nucleus of the atom. name and identify and subatomic particle that surrounds the nucleus of the atom. describe the properties of the subatomic particle that surrounds the nucleus of the atom. define atomic number and identify what element it represents using the periodic table identify the element symbol with a given atomic number. define isotope and draw a nucleus of an atom’s particular isotope. identify the differences and similarities between isotopes of the same atom. define mass number and correctly write the symbol and name of an atom’s particular isotope. Ch 4 Related assignments: Back to Basics Atom quiz p 91 #2, 5; p97 #7, 8, 9 Ch 4 test Rutherford’s experiment p 99 #11-13; p101 #14; p104 #18 - 21 Back to Basics Atom quiz Main ideas: Atomic structure – protons, neutrons, electrons # protons identifies an atom Isotope – atom with a different number of neutrons Ion – atom that has lost or gained an electron(s) Nuclear reactions involve the nucleus and thus change the ID of an atom Indirect measurement of electrons, aka Rutherford’s experiment Follow up questions: 1. What does it mean to measure something indirectly? 2. What does this have to do with atoms? Atomic theories – the old stuff – use online or your textbook to fill in A – G. Due __ A: Democritus’s Ideas - dates lived: Matter is ___________________________________ Atoms are ________________________________________ Different properties of matter are due to ______________________________ Changes in matter depend on _________________________________ B: Aristotle’s Ideas - dates lived: Did not believe in ______________________________________ Did not like __________________________ideas and renounced them More popular thinker so Democritus’s ideas were knocked out for ________ years! C: John Dalton - dates lived: Matter is made of _________________________________ All atoms of an element are _____________________________________ Atoms cannot be _________________________________ In a chemical reaction, atoms are __________________________________ D: J.J. Thompson - date of discovery: Accidentally discovered ___________________ What is a Cathode Ray Tube? ______________________________________ _______________________________________________________________ Draw a picture of a Cathode Ray Tube E: Plum pudding theory, aka the chocolate chip cookie theory – electrons disbursed evenly throughout an atom like chocolate chips in batter. Draw a model for this theory and label the electrons. F: Rutherford - date of discovery What did Rutherford do? Discovered evidence of __________________________ Label the drawing with Radioactive source Alpha particle stream Gold foil Detecting screen What is the charge of an alpha, α, particle? If the gold atoms had evenly distributed electrons, like the Plum Pudding model suggested, all the positive charge would have gone straight through. They didn’t. They bounced in all different directions. Why? (Remember: different attracts, like repels) G: Nuclear Model Label each diagram below as either a Plum Pudding Model or a Nuclear Model + charge alpha + charge alpha electron + charge alpha electron + charge alpha Stop filling in notes on your own here Atom parts Really, really, really _____ World population is _____________________ people One penny has ______________________________________copper atoms in it Atom size demo The Atom’s Family Nucleus – Located _________________________________ Always has a ____________________ charge Made of protons o Mass of _____ o Charge of ________ o DETERMINES THE IDENTITY OF AN ATOM And neutrons o Mass of __________ o Charge of __________ o Joke: a neutron walks into a bar and orders a drink. He asks the bartender how much. The bartender answers “For you? ______________________” # of protons does _____ have to equal # of neutrons. VERY _________. If nucleus was the size of a period on this page, it would weigh = to _______________ _______% of atom’s _______ Surrounded by the __________________________ Atom is mostly ______________________. Size of the atom is _______________ the size of the nucleus. About the same as a ___________ compared to the size of a _________________. Electrons Moves 2/3 the speed of light around the nucleus Mass of _________________ Charge of _________________ In a NEUTRAL atom, number of electrons always _______________________________ Addition or subtraction of electrons is a ___________________________________ Example: Summarize atomic structure in three sentences 1. 2. 3. HW p91 #2, 5 p97 #7, 8, 9 Characteristic of atoms All atoms of one type of element share some characteristics. On periodic chart, looks like… # of protons = # electrons in neutral atom Mass of nucleus: protons + neutrons Chemical name - self explanatory Atomic number = _________________________ THIS IS WHAT IDENTIFIES AN ELEMENT! Symbol – 1, 2, or 3 letters, first always __________________. Why? Mass – average mass of NEURTONS + PROTONS Measured in amu – atomic mass unit Not exactly the same as the number of neutrons + number of protons because of isotopes (see next page). For our ID purposes, round off to the nearest ______________________. Number of neutrons = mass minus atomic number (big # - little #) i.e. Number of neutrons = Remember, normal single atoms are electrically __________ b/c ___________________. Atom changes Ion An atom that has __________________________________ Can be _______________ or _______________ DOES have a __________________________ Joke: two ions are walking down the road. One says “I think I lost an electron”. The other says “Are you sure?” The first one answers “Yea, I’m __________________” Isotopes Atoms with same number of protons and electrons but different numbers of ____________________. o Charge of atom _______________ o Identity of atom _______________ o Chemical behavior ________________ o Mass of atom _____________ naturally occurring ways to write isotopes o name and mass example: gold – 198 hydrogen – 2 what does the number represent? o mass/number and symbol example: 198 2 79 Au 1 H what does the top number represent? What does the bottom number represent? Practice: Name Atomic # Oxygen 8 Zinc 30 HW p99 #11-13 Protons Electrons Neutrons 82 82 125 8 16 30 35 11 11 p101 #14 Atomic mass Mass/number symbol p104 #18 - 21 Test here!! Chapter 25: Nuclear Reactions CHEM 12 understand the basic processes of nuclear chemistry. You can Demonstrate the use of symbols, formulas, and equations in describing nuclear reactions. Explain and balance nuclear equations. Compare fission and fusion reactions in terms of the masses of the reactants and products and the amount of energy released in the nuclear reactions. Ch 25 Related assignments: HW p106 #23 – 27 Ch 4 test Nuclear ws Nuclear testing video - http://en.wikipedia.org/wiki/Nuclear_weapons_testing Bikini Island - http://www.sonicbomb.com/modules.php?name=Content&pa=showpage&pid=61 Nuclear reactions A change in the ____________________ A chemical change involves electrons only and does not alter the nucleus Atom nuclei decay (break apart) or combine to __________________________________ o Remember, protons determine the identity of an atom. Involves ENORMOUS amounts of energy Fusion o Two of more nuclei ____________________________ o Produces one NEW element o The result of an extremely high energy collision o Occurs in _________ o We have not mastered this process yet. Fission o A nuclei _____________________________ o Produces two or more NEW elements o The result of an unstable ratio of neutrons to protons in the nucleus o Happens spontaneously o Used in ______________________ and ______________________ Radiation – the energy or particles released in a nuclear reaction Radioactivity – the process of releasing radiation Review: If two atoms are put together to make one, what is the process called? How do you know the identity of an atom? What are three ways to tell if a reaction is chemical or nuclear? Nuclear ws Alpha radiation decay Occurs spontaneously in atoms with an atomic number greater than ______ Alpha particles – two protons and two neutrons are physically ejected from the atom o Which atom has 2 protons and 2 neutrons? Charge Symbol – Used by ______________________ Blocked by paper Nuclear equation for alpha radiation – 21084 Polonium 20682Lead + 42He Negative Beta radiation Happens when there are ______________________________________ Beta particles – an electron is physically ejected from the nucleus o Hey, wait a minute, there aren’t electrons in the nucleus o Neutron splits into a positive proton that stays in the nucleus and a negative electron that is shot out Charge – Symbol – Blocked by metal foil Nuclear equation for negative beta radiation – 146Carbon 147nitrogen + 0-1β o Notice: atomic number goes _____ while atomic mass is _______________. Remember, atomic number is how many protons. Atomic mass is the total of protons and neutrons. One neutron becomes one proton. Positron emission/Positive Beta radiation Happens when there are too many _____________________ Proton sheds its positive aspect and becomes neutral – a neutron The ‘positive aspect’ is called a positron and it radiates from the nucleus. Happens when there are ______________________________________ Blocked by metal foil Gamma radiation rays of very high energy No actual particles radiating from the atom. No change in atom’s composition or identity. Millions are going through you right now! Not blocked by lead or concrete How’d they figure all this out? The diagram shows the paths of alpha, negative Beta, positive Beta, and Gamma radiation. Positive plate Radiation source Negative plate screen What are the charges for each type of radiation? α ββ γ A woman’s turn – one of the most influential people in the history of nuclear research is Marie Currie. Marie and her husband Pierre began studying nuclear chemistry in the late 1880’s. Together they won a Nobel Prize in physics. After her husband died in 1906 she went on to win a second Nobel Prize, this time in chemistry. She is the only person to ever win a Nobel Prize in both physics and chemistry. Because radiation was only being discovered during her research, there was a lack of understanding that protection from radiation exposure was needed. Madame Currie died from radiation poisoning in 1934. Her accomplishments include developing a theory of radioactivity (she coined the term, too), isolating isotopes, discovering Polonium and Radium and beginning the research into cancer treatments. Review If a radiation product is made of two neutrons and two protons, what kind of radiation was it? What do the numbers in front of the radiation symbols, such as α, mean? What are three ways to tell if a reaction is negative Beta? HW p106 #23 - 27 Test here!!