Notes Ch. 4 and 25: Atomic Structure and Nuclear Chemistry History and Structure of the Nuclear Atom

The Atom • smallest particle of an element that retains all properties of the element I. Early Models of the Atom A. Democritus (460 B.C. – 370 B.C) • first to suggest the existence of ______• believed atoms were indivisible and indestructible B. Dalton • Atoms of the same element are ______• Each element is unique • Atoms combine in fixed ratios to form compounds C. Thomson • Discovered ______• Suggested atom looked like plum pudding (or a blueberry muffin or chocolate chip cookie) with electrons evenly distributed throughout positive sphere D. Rutherford • Conducted gold foil experiment • Proposed atom is mostly empty space • Concluded all positive charge and mass is concentrated in small region called ______E. Bohr • depicts the atom as a small, positively charged nucleus • surrounded by electrons that travel in circular ______around the nucleus F. Schrödinger • model allowed the electron to occupy three-dimensional space like an electron “______” • Used a mathematical equation to show a model of electrons as waves II. More about the Atom A. Size • Teeny tiny • observable with instruments such as a scanning tunneling ______

B. Parts (called Subatomic Particles)

1. Protons: p+ 2. Electrons: • mass ~ 0 • charge = e- 3. Neutrons: no positive +1 • charge = • charge = zero • mass = 1 negative -1 • mass = 1 C. D. Location of Parts • Nucleus: center of atom E. - contains protons and neutrons F. - has a positive charge G. - contains almost ALL of the ______of the atom • Outside nucleus: H. - contains ______I. - has a negative charge J. - occupies almost ALL of the volume of the atom K. L. Atomic Charge • ______are NEUTRAL • # of protons = # of electrons 1 M. (ALWAYS if you’re talking about an ATOM) N. How Atoms Differ I. Properties of Subatomic Particles O P Q. Location R T U. Actual mass . . . . (g) P S R R V A W Z -28 . Y. A AB. 9.11 x 10 E . . . A A A A -24 C AF. H AI. 1.673 x 10 . D G . A A A AM. In the A J O AP. 1.675 x 10-24 K nucleus . N . . AQ.N . II. Atomic Number • the number of ______in an atom • Identifies element – each atom has unique # – # never changes III. Mass number • represents the ______of the number of ______and neutrons in the nucleus • # of neutrons = mass number – atomic number IV. Isotopes • Atoms of the same element but have a different # of neutrons • Ex: 3 isotopes of carbon: Carbon-12, Carbon-13, Carbon-14 AR. ____# protons, ____# protons, ____ # protons AS. ____# neutrons, ____# neutrons, ____ # neutrons • All elements have isotopes (some 2, some 3, etc.) • Some isotopes are naturally radioactive. • Ex: Plutonium V. Representing Isotopes • In Ag-107, the 107 represents the mass number (neutrons + protons) • the 47 represents the number of protons) AT. Practice: AU. 1. What is the mass number for Co-59? AV. 2. What is the mass number for ? VI. Atomic Mass • The standard is the atomic mass unit (amu): defined as 1/12 of the mass of a carbon-12 atom • the weighted average of the isotopes of that element. • Formula: A AZ. B B BJ. B B BT. W A. E K. O . % . % . A m m B B A B. B L. B X of F of P . B . B . o o a C. M Is . B B G Q Is . . Is I

BU. Practice 3 • Silver has two naturally occurring isotopes. Ag-107 has an abundance of 51.82% and mass of 106.9 amu. Ag-109 has a relative abundance of 48.18% and a mass of 108.9 amu. Calculate the atomic mass of silver. BV. BW. BX. BY. BZ. Practice 4 • Rubidium is a soft, silvery-white metal that has two common isotopes, and . If the abundance of 85Rb is 72.2% and the abundance of 87Rb is 27.8%, what is the average atomic mass of rubidium? CA. CB. CC. CD. CE. CF. Vocabulary to Know • Atomic #- same # of protons & electrons • Mass #-protons + neutrons CG. written 2 ways: Carbon-14 or C • Isotopes-same # of protons, different # of neutrons • Atomic mass-weighted average mass CH. CI. Types of Radiation and Unstable Nuclei CJ. CK. I. Chemical and Nuclear Reactions • Chemical reactions only involve an atom’s ______• ______reactions involve changing an atom’s nucleus • Nuclear reactions release about a ______times more energy than chemical reactions • Unlike chemical reaction, nuclear reactions are not affected by ______, pressure, or a catalyst. CL. CM. II. Nuclear Vocabulary • Radioactivity – the process of emitting ______• Radiation - ______and particles emitted by a radioactive source. • Radioisotopes – ______of atoms with unstable nuclei and emit radiation to obtain a more stable nuclei • Radioactive decay -______nuclei losing energy by emitting radiation in a spontaneous process. • Nucleon – refers to both ______and neutrons CN. CO. III. Which Isotopes are Radioactive? • Small Nuclei - Atoms which contain up to ______protons (up to Calcium) are usually ______. • Large Nuclei - Larger nuclei tend to be ______. All nuclei with ______or more protons (Polonium and up) are radioactive. For example, all isotopes of Uranium are radioactive. • 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 (6 protons and 6 neutrons) is stable, while ______(6 protons and 8 neutrons) is radioactive. CP. 3 CQ. IV. Why Does an Atom Undergo Radioactive Decay? • Radioactive atoms emit radiation because their nuclei are ______. • The stability of the nucleus depends on the ______to ______ratio • Neutrons vs. protons graph stable nuclei found in a region called the band of ______. CR. CS. V. Types of Radiation – Alpha Radiation • Alpha radiation are attracted to the negatively charged plate • Alpha particles contain two protons and two neutrons (A ______nucleus) • Blocked by______• Least penetrating form of radiation (only travels a few centimeter in the air) • Carry +2 charge • Symbolized by ______or a CT. CU. VI. Types of Radiation – Beta Radiation • Beta radiation attracted to the positively charged plate • Carry –1 charge • Beta particles are fast moving ______• Blocked by metal foil or ______• Medium penetration power (travels a few meters in the air) • Symbolized by _____ or b CV. CW. VII. Types of Radiation – Gamma rays • Gamma rays are high energy radiation that possesses no ______. • Possess no electrical charge and are not deflected by magnetic or electrical fields. • Not completely blocked by lead or ______• The most penetrating and damaging type of radiation • Carry no charge • Symbolized by ______CX. CY. VIII. Electron Capture • Electron capture occurs when a nucleus of an atom draws in an ______. • Rb + e → Kr CZ. • Also known as ______capture DA. DB. IX. Electrostatic Force • Electrostatic force is when like charges ______and opposite charges ______. DC. X. Strong Nuclear Force • that are extremely ______together. It keeps the nucleus ______. DD. Remember Mass Number and Atomic Number  DE. XI. Writing and Balancing Nuclear Equations • In a balanced nuclear equation, mass numbers and atomic numbers are ______. DF. Example DG. Th à Ra + He – Notice the mass numbers and atomic numbers add up to the same on both sides of the equation DH. Practice

1. Zr à e + ? DI. DJ. 2. Po à He + ? DK. DL. 3. ? à Rn + He DM. DN. 4. Ca à e + ? DO. DP. 5. Cm à He + ? DQ.Transmutation DR. I. Transmutation • Transmutation - The conversion of one element to ______element. • All nuclear reactions are transmutation reactions except for ______emission, which does not alter an atom’s atomic number. II. Induced Transmutation • Before 1919, the only way to change the nucleus or cause transmutation was to wait for ______. • In 1919 Rutherford was the first to induce (______) transmutation. • He proved that nuclear reactions can be produced ______. • Induced transmutation can occur by ______an atom with alpha particles, protons or neutrons. III. Transuranium Elements • Elements with atomic number above ______. • All transuranium elements undergo transmutation • None of the transuranium elements occur in ______and have only been produced through induced transmutation. DS. IV. Half-life • The time required for ______of a radioisotope’s nuclei to decay into its products • After each half-life, half of the existing radioactive atoms have decayed into atoms of a ______element • Amount remaining at time T = (initial amount)(1/2)n DT. where n= number of half-lives • n = total time ÷ time of one half-life DU. DV. Practice 1. Scientists start with 50.0 g sample of a radioisotope. How much is left after four half-lives? DW. DX. DY. DZ. EA. EB. 2. 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 2.000 mg sample will remain after 133.5 days? EC. ED. EE. EF. EG. EH. V. Carbon-14 Dating 5 • Carbon 14 dating is the process of determining the ______of artifacts that were once part of a living organism by measuring the amount of 14C ______in that artifact • Carbon-14 is radioactive and undergoes beta decay. It has a half-life of 5730 years. EI. Carbon-14 • 14C evenly spread in the Earth’s biosphere • Plants incorporate 14C into their structure that matches the level in the atmosphere. • When an organism dies, 14C declines at a known rate. (Half-life of C-14 = 5730 years) • Comparing the remaining 14C fraction of a sample to that expected from atmospheric 14C allows the age of the sample to be estimated. • Dates carbon-bearing materials up to 62,000 years. • Carbon-14 Decay EJ. EK. EL. EM. EN. EO. EP. EQ. ER. ES. ET. EU. EV. • Using the graph, about what % of carbon-14 remains after 11, 400 years? EW. EX. EY. Fission and Fusion of Atomic Nuclei EZ. I. Nuclear Fission • Fission - The splitting of the nucleus into ______(division) • Uranium-235 is struck by a neutron and forms Ba-141, Kr-92, and additional neutrons. FA. II. Chain Reaction • Chain reaction – Nucleus captures a neutron and splits into fragments and produces three neutrons – ______start a new reaction • Critical mass – The ______mass required to support a self-sustaining chain reaction FB. III. Nuclear Fusion • Fusion - ______atomic nuclei to produce a nucleus of greater ______• Fusion reactions release ______energy than fission reactions • The ______is powered by fusion FC. IV. Nuclear Binding Energy • The energy required to break a nucleus into its individual protons and neutrons • Energy released in a nuclear reaction is much ______than in chemical reactions FD. V. Mass Defect • When breaking apart a nucleus, there is a change in mass called the mass defect. • The change in mass was converted to energy. • We know this as E=mc2 FE. VI. Nuclear Reactors • The purpose of nuclear reactors is to keep the chain reaction going without letting it get out of control FF. VII. Nuclear Bombs FG. Atomic Bomb • Uses______• Uses enriched uranium-235 or plutonium • Nagasaki and Hiroshima FH. Hydrogen Bomb • Uses ______• 1000 time more powerful than atomic bomb • Uses deuterium 2H and tritium 3H

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