Structure of the Nuclear Atom

Transcription

1 Structure of the Nuclear Atom I. The II. A. The is the smallest particle of an element that retains its of the element. History of the Atom A. Democritus 1. Democritus (460 B.C. 370 B.C) was the first to suggest the of atoms 2. Democritus believed atoms were and B. Dalton s Atomic Theory 1. All elements composed of particles called atoms 2. Atoms of the same element are 3. Atoms of different elements can physically mix together or combine in simple whole-number ratios to form. 4. Chemical occur when atoms are separated, joined, or rearranged. lll. Size of the Atom A. The radii of most atoms range from m to m B. Individual atoms are observable with instruments such as a scanning tunneling. What is an atom? Who is Democritus? What are the four ideas of Dalton s Atomic Theory? What is the size of most atoms? What do scientists use to see an atom? lv. Atoms and Their Charges A. Atoms have electrical charge, they are electrically B. Electric charges are carried by particles of matter ( particles) C. Electric charges always exist in multiples. (no fractions) D. When a given number of charged particles combines with an equal number of charged particles, an electrically particle is formed V. Subatomic Particles A. There are three kinds of subatomic particles. These particles make up the atom. 1. (negative) 2. (positive) 3. (neutral) B. Electrons 1

2 1. Electrons are charged 2. One electron carries of negative charge 3. Has a mass of 1/1840 of a 4. Symbol for and electron is C. Protons 1. Protons are charged subatomic particles 2. Each proton has a mass about 1840 times that of an 3. Symbol for a proton is D. Neutrons 1. Neutrons are subatomic particles with 2. Has a mass equal to that of a 3. Symbol for a neutron is What charge are atoms? Are there fraction of charges? What if there were nine positively charged particles and eight negatively charged particles, what would the net charge of the atom be? What are the three subatomic particles and what are their charges? What is the mass of an electron compared to a hydrogen atom? What is the mass of a proton compared to a neutron? Vl. J.J. Thompsons s Plum Pudding Model A. When subatomic particles were discovered, scientist wondered how these particles were put together in an atom. B. J.J. Thompson thought that were evenly distributed throughout. An atom was filled uniformly with charged material called the plumpudding model or chocolate cookie dough model Vll. Rutherford s Gold Foil Experiment A. In Ernest Rutherford wanted to study the structure of the atom as well. The plum-pudding model was the prevailing theory back then B. In his experiment he used alpha particles, which are atoms that have lost their two electrons. C. Then, directed the alpha particles at a very thin sheet of gold foil. The particles should have passed easily through the gold with a slight deflection due to the charge thought to be spread out in the gold atoms D. The great majority of alpha particles passed straight through the gold atoms, without E. A small fraction of the alpha particle bounced off the gold foil at angles. F. Based on the experimental results Rutherford suggested that the atoms were mostly, but had a called the. 2

3 G. Gold Foil Experiment Conclusion 1. All the charge and all the of the atoms was concentrated in a small region called the 2. This is almost as incredible as if you fired a 15-inch shell at a piece of tissue paper and it came back and hit you. Vlll. The Nuclear Atom A. The nucleus is the central core of an atom 1. composed of and. B. The nucleus is much smaller than the atom, yet contains most of its C. The are distributed around the nucleus 1. occupy almost all the of the atom 2. Most of the atom is made up of. lx. Fun Facts A. The volume of a hydrogen nucleus is a trillion times smaller than the volume of a hydrogen atom, yet the nucleus contains most of the mass. B. If the nucleus (proton) of a hydrogen atom were as large as the width of a human thumb, the electron would be on the average about one kilometer away in a great expanse of empty space. What is the plum-pudding model and who thought of it? Is the plum-pudding model correct? What happened in the gold foil experiment? What did the gold foil experiment prove? Where is the positive charge located in the atom? What contains most of the mass of the atom? What occupies most of the volume of the atom? What is the atom is mostly made up of? How Atoms Differ I. Properties of Subatomic Particles Particle Symbol Location Relative Relative Actual Mass (g) Charge Mass Electron In the space e or surrounding the 1-1/ nucleus Proton p + or In the nucleus Neutron n o or In the nucleus

4 II. Atomic Number A. The atomic number is the number of or electrons in a atom B. Remember that atoms are neutral thus: 1. Atomic number = Number of = number of C. Each has a unique number of protons D. The periodic table is organized by increasing (number of protons) E. Only protons determine the type of atom present and will never change for an. What does the atomic number represent? Why are there an equal number of protons and electrons in a neutral atom? How many protons and electrons are in aluminum (Al)? An atom contains 28 protons, what element is it? How many electrons does it have? How is the periodic table organized? What subatomic particle determines the type of element? III. Isotopes and Mass Number A. Isotopes are atoms of the same element that have the same number of but different number of B. Mass number represents the sum of the number of and in the nucleus C. So, # of neutrons = IV. Representing Isotopes A. In Ag-107, the 107 represents the mass number (neutrons + protons) B. In Ag-109, the 109 represents the mass number (neutrons + protons) What are isotopes? What is the mass number? What is the mass number in carbon-14? What is the mass number and atomic number in Fe? How many protons, neutrons, and electrons are in potassium-41, whose symbol is K? How many protons, electrons, and neutrons are in Ne? What is the difference between hydrogen ( H), deuterium ( H), and tritium ( H)? V. Atomic Mass A. The mass of an atom is so small it is difficult to work with, so chemists have developed an to compare all the masses to B. The standard is the atomic mass unit (amu) is defined as of the mass of a atom 4

5 C. If the mass of an element is not close to a whole number, it is because the atom has several D. The atomic mass is the weighted average of the of that element. VI. Example A. Silver has two naturally occurring isotopes. Ag-107 has an abundance of 51.82% and mass of amu. Ag-109 has a relative abundance of 48.18% and a mass of amu. Calculate the atomic mass of silver. Rubidium is a soft, silvery-white metal that has two common isotopes, Rb and Rb. If the abundance of 85 Rb is 72.2% and the abundance of 87 Rb is 27.8%, what is the average atomic mass of rubidium? VII. Vocabulary to Know A. Atomic #- same # of protons & electrons B. Mass #-protons + neutrons written 2 ways: Carbon-14 or C C. Isotopes-same # of protons, different # of neutrons D. Atomic mass-weighted average mass Types of Radiation and Unstable Nuclei I. Chemical and Nuclear Reactions A. Chemical reactions only involve an atom s B. Nuclear reactions involve changing an atom s C. reactions release much more energy than reactions 1. about a million times more energy D. Unlike chemical reaction, nuclear reactions are not affected by, pressure, or a. II. Nuclear Vocabulary A. the process of emitting radiation. B. - rays and particles emitted by a radioactive source. C. isotopes of atoms with unstable nuclei and emit radiation to obtain a more stable nuclei D. Radioactive - Unstable nuclei losing energy by emitting radiation in a spontaneous process. E. refers to both protons and neutrons What is the difference between a chemical reaction and a nuclear reaction? Which type of reaction is affected by temperature, pressure, and a catalyst? Which type of reaction releases more energy? What is radiation? What is radioactivity? 5

6 What is a radioisotope? What is radioactive decay? What is a nucleon? III. Which Isotopes are Radioactive? A. Small Nuclei - Atoms which contain up to 20 protons (up to Calcium) are usually. B. Large Nuclei - Larger nuclei tend to be radioactive. All nuclei with or more protons (Polonium and up) are radioactive. For example, all isotopes of Uranium are radioactive. C. Atoms with more neutrons than protons - There are radioactive nuclei that have less than 84 protons. These nuclei have more neutrons than protons. For example, Carbon-12 ( protons and neutrons) is stable, while Carbon-14 ( protons and neutrons) is radioactive. IV. Why Does an Atom Undergo Radioactive Decay? A. Radioactive atoms emit radiation because their nuclei are. B. The stability of the nucleus depends on the neutron to proton C. Neutrons vs. protons graph stable nuclei found in a region called the V. Types of Radiation Radiation A. radiation deflect toward the negatively charged plate B. Alpha particles contain protons and neutrons (A helium nucleus) C. Blocked by paper D. Least penetrating form of radiation (only travels a few centimeter in the air) E. Carry charge F. Symbolized by He or α VI. Types of Radiation Radiation A. radiation deflect toward the positively charged plate B. Carry charge C. Beta particles are fast moving D. Blocked by metal foil or wood E. Medium penetration power (travels a few in the air) F. Symbolized by e or β VII. Types of Radiation Gamma rays A. Gamma rays are high energy radiation that possess. B. Possess electrical charge and are not deflected by or electrical fields. C. Not completely blocked by lead or concrete D. The most penetrating type of radiation E. Carry charge F. Symbolized by γ 6

7 VIII. Positron Emission A. A particle with the same mass as an electron but opposite charge. B. Symbolized by e or β C. C + e IX. Electron Capture A. Electron capture occurs when a of an atom draws in a surrounding electron. B. Rb + e Which elements are radioactive? Why does an element undergo radioactive decay? What makes a nucleus unstable? What is the band of stability? What does an alpha particle also known as? Is an alpha particle positive or negative? What blocks alpha particles? Is a beta particle positive or negative? What blocks beta radiation? Is a gamma ray positive or negative? What blocks gamma rays? X. Electrostatic Force A. Electrostatic force is when like charges and opposite charges. XI. Strong Nuclear Force A. All nuclei except H atoms consist of neutrons and two or more protons. Since protons are, the two positive charges should because of electrostatic repulsion. B. The protons do not repel each other because of the strong force. C. The strong nuclear force or nuclear force is an attractive force that acts between all that are extremely close together. It keeps the together. What is an electrostatic force? What happens when two positive charges are close together? What is the strong nuclear force? Remember Mass Number and Atomic Number XII. Writing and Balancing Nuclear Equations A. In a balanced nuclear equation, numbers and numbers are conserved. B. Example Th Ra + He **Notice the mass numbers and atomic numbers add up to the same on both sides of the equation 7

8 Zr e +? Po He +?? Rn + He Ca e +? Cm He +? Transmutation I. Transmutation A. The of one element to another element. B. All nuclear reactions are transmutation reactions except for emission ll. Induced Transmutation A. Before 1919, transmutation only occurred B. In 1919 was the first to induce (cause) transmutation. C. He proved that nuclear reactions can be produced artificially. D. Induced transmutation can occur by bombarding an atom with particles, protons or neutrons. III. Transuranium Elements A. Elements with atomic number above. B. All transuranium elements undergo transmutation C. None of the transuranium elements occur in and have been produced through induced transmutation. What is transmutation? Which reactions are transmutation reactions? What is induced transmutation? Before Rutherford, how could an element undergo transmutation? What are transuranium elements? IV. Half-life A. The time required for one-half of a radioisotope s nuclei to decay into its B. After each half-life, of the radioactive atoms have decayed into atoms of a new element C. Amount remaining = (initial amt)(1/2) n 1. n= Scientists start with 50.0 g sample of a radioisotope. How much is left after four half-lives? Iron-59 is used in medicine to diagnose blood circulation disorders. The half-life of iron 59 is 44.5 days. How much of a mg sample will remain after days? 8

9 V. Carbon-14 Dating A. Carbon 14 dating is the process of determining the of artifacts that were once part of a living organism by measuring the amount of remaining in that artifact B. Carbon-14 is radioactive and undergoes decay. It has a half-life of VI. Carbon-14 A. 14 C evenly spread in the Earth s B. Plants incorporate 14 C into their structure that matches the level in the. C. When an organism dies, 14 C declines at a known rate. ( of C-14 = years) D. Comparing the 14 C fraction of a sample to that expected from atmospheric 14 C allows the age of the sample to be. E. Dates carbon-bearing materials up to years. What is radiochemical dating? How does carbon-14 dating work? VII. Radioactive Glassware A. Fission and Fusion of Atomic Nuclei I. Nuclear A. - The splitting of the nucleus into fragments (division) B. Uranium-235 is struck by a neutron and forms,, and additional neutrons. II. Chain Reaction A. Nucleus captures a and splits into fragments and produces three neutrons B. start a new reaction C. Critical mass 1. The minimum required to support a self-sustaining reaction III. Nuclear A. - combining atomic nuclei to produce a nucleus of greater mass B. the nuclei of lighter elements (such as hydrogen) are fused together at extremely high and to form heavier elements (such as helium) C. Fusion reactions release more than fission reactions D. Capable of releasing large amounts of energy E. Requires extremely high energies to and sustain F. is powered by fusion What is fission? What products are formed in the fission of uranium? What is a chain reaction? 9

10 What is critical mass? What is fusion? Where do we find fusion? IV. Nuclear Binding Energy A. The energy required to break a nucleus into its individual and B. Energy released in a reaction is much greater than in reactions V. Mass Defect A. The mass of the nucleus is always than the sum of the masses of individual protons and. B. The difference in mass has been converted to C. The energy can be calculated using What is the nuclear binding energy? Which releases much more energy nuclear or chemical reactions? What is the mass defect? What equation can be used to calculate the mass defect? VI. Nuclear Reactors A. The purpose of nuclear reactors is to keep the going without letting it get out of control VII. Bombs A. Atomic Bomb 1. Uses 2. Uses enriched uranium-235 or 3. Nagasaki and B. Hydrogen Bomb 1. Uses 2. time more powerful than atomic bomb 3. Uses deuterium and tritium What is the purpose of nuclear reactors? Which is more powerful, an atomic or hydrogen bomb? 10