Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
video 2 .4 atomi c th e o ry democritus (460-370bc) Greek philosopher ! His model of the atom: ! ! ! Coined the term “______” - atomos john dalton (1808) English scientist ! His model of the atom: ! All elements composed of tiny particles called ATOMS ! Atoms of same element are ___________; atoms of different elements are different ! Atoms are the __________ piece that any substance can be broken down into j.j. thomson (1897) Discovered ___________ using a cathode ray tube ! His model of the atom: ! called “plum pudding” model ! Atom is ____________ charged with negative electrons embedded in it ! Dalton’s Model: Solid, indestructible sphere 1 ernest rutherford (1911) Discovered the _____________ with his famous Gold Foil experiment ! His model of the atom: ! Small, dense, __________ nucleus ! Made of mostly _______________ ! rutherford’s gold foil experiment The experiment: Positively charged alpha particles were shot at a thin sheet of gold foil. ! The result: ! Most particles went _______________. ! A few were _______________ ! rutherford’s gold foil experiment ! His Conclusion: (you must know this) Atom is mostly _____________________ ! Atom has small, dense, __________ nucleus ! example ! When alpha particles are used to bombard gold foil, most of the alpha particles pass through undeflected. This result indicates that most of the volume of a gold atom is made of________. 1. 2. ! 3. ! 4. ! ! a nucleus neutrons protons unoccupied space 2 niels bohr (1913) ! wave mechanical model / electron cloud model His model of the atom: Electrons travel around the nucleus in welldefined paths called ___________ (like planets in a solar system). ! Electrons in different orbits have different amounts of _____________. ! The further from the nucleus, the more __________ an electron has. ! Present-day model of atom ! Can not determine an exact location of an electron, only the ______________ of finding an electron in a certain place at a certain time. ! ____________: region where an electron is most likely to be found ! 3 video 2 .5 subat omic partic les subatomic particles parts of the atom atomic number Equal to the number of __________ ! Every element has its own atomic number ! Periodic table is arranged based on atomic number ! Electron Shells ________ 1 mass number The sum of the _________ and ____________(whole number) ! Can be written as carbon-12 to find number of protons ! ! Look up ___________on periodic table ! Ex. Lithium has ______ protons to find number of electrons Equal to the _______________in a neutral atom ! Ex. Lithium has ______ electrons ! to find number of neutrons Protons + Neutrons = Mass Number ! Neutrons = ________________________ ! Ex. Lithium has ____ neutrons (7-3 = 4) ! 2 to find nuclear charge ! Equal to the _________________ ! Ex. Lithium has a ______nuclear charge example: fill in the table ions Ions: ____________ particles ! Formed when atoms gain or lose _______ ! cations The atom loses electrons and becomes _____________ charged ! Ex. Na+ ! Na Atom: 7p+ 7e(neutral) Na+ Ion: 7p+ 6e(+1 charge) 3 anions example The atom gains electrons and becomes _____________ charged ! Ex. Cl! Cl Atom: 17p+ 17e(neutral) Cl- Ion: 17p+ 18e(-1 charge) 4 video 2 .6 isotop averag es and e atom ic mass complete chemical symbols isotopes ! Elements that have the same atomic number, but different __________ (different numbers of ______________) common isotopes of hydrogen Show the mass # and atomic # of element ! Isotopes will have the same ________ #, but different __________ #’s ! 1 example example ! The chemical symbol of carbon-14 ! Write the chemical symbol for oxygen-17: ! How many neutrons does it have? ! How many neutrons does it have? calculating average atomic mass ! example of a weighted average Why is atomic mass not a whole number? The atomic mass on the periodic table is a __________________of the naturally occurring ______________ of that element. ! The atomic mass takes into account the relative _____________ of the naturally occurring isotopes of the element. ! 2 example: determining avg atomic mass Boron-10 19.78% 10.013amu Boron-11 80.22% 11.009amu Step 1: Multiply the mass of each isotope by the percent abundance IN DECIMAL FORM (move decimal 2 spots to the LEFT) example Determine the average atomic mass: Potassium-39 93.12% 38.964amu Potassium-41 6.88% 40.962amu ! Step 2: Add the products from Step 1 3 video 2 .7 bohr d iagram bohr models The greater the distance from the nucleus…the greater the __________ of the electrons in that shell (energy level) ! The orbits are called principal energy levels or ____________ ! bohr models ! s How do electrons orbit the nucleus? ! ! In ___________________ Each principal energy level: Is a __________ distance from the nucleus ! Can hold a specific number of electrons ! Has a definite amount of energy ! how many electrons can each shell hold? 2n2 ! n = the ____________ number from the periodic table or shell number ! Ex. Max # of electrons in 1st shell is: ! ! 2 (1)2= ______ electrons Increasing energy 1 drawing bohr diagrams example: bohr diagram of mg Look up electron configuration on periodic table (if it is an ion, add/subtract electrons from outermost shell) ! Draw a circle for the nucleus and notate number of protons and neutrons in it. ! Draw energy levels and notate number of electrons in each shell. ! example: bohr diagram of mg+2 example: bohr diagram of ca+2 2 video 2 .8 ground state vs. excite d stat e and bri gh t l i spectr ne a example ! Possible excited states for Na: ground state vs. excited state Ground state: when electrons occupy the ____________ available energy levels (the configuration on the periodic table) ! Excited state: electrons no longer occupy the lowest energy levels. One or more electrons ________ to a higher energy level (different than electron configuration on PT). ! how do you tell if the configuration is ground or excited state? Add up total number of electrons in configuration ! Determine element ! If it matches element’s configuration on periodic table = ______________ ! If it doesn’t match = _____________ ! 1 example ! Identify the following electron configuration as being ground state or excited state: 2-6-1 bright line spectra ! Absorption: Electrons ________ energy as they move to __________ energy levels (excited state). ! This excited state is temporary and __________. ! Electrons eventually fall back down to ground state. ! 2 + 6 + 1 = _______ ! 9 electrons = _____________ ! Must be ______________ STATE ! bright line spectra ! Emission: ! Electrons are negatively charged and therefore attracted to the positive nucleus, so they eventually fall back to the ground state and __________ energy in the form of _____________. bright line spectra ! Light: ! The color of the light is determined by the amount of energy released by the electron when it drops back down to the ground state 2 bright line spectra ! ! ! The different colors of light emitted produce a pattern called a bright line spectrum. Each element has a ____________ bright line spectrum (like a fingerprint) Bright line spectra can be used to ___________ unknown samples of elements example ! What elements make up the unknown sample? 3 video 2 .9 lewis dot diagram s lewis dot diagrams Electron dot diagrams ! Only show ____________ electrons ! Valence shell: _____________ shell of an atom that contains electrons ! Valence electrons: electrons that occupy the valence shell (last number in electron configuration) ! steps to draw dot diagrams Draw the element’s symbol ! Locate valence electron number (last number of electron configuration) ! Draw dots around the element’s symbol to represent the number of valence electrons ! example ! Draw the dot diagram for Carbon C 1 example ! Draw the dot diagram for Sodium Na lewis dot diagrams: ions Draw brackets around the element symbol ! Write charge of ion outside of bracket in top right corner of symbol ! Positive ions: NO dots ! Negative ions: 8 dots ! Na = 2-8-1 Na+ = 2-8 example ! Draw the dot diagram of K+ example ! Draw the dot diagram of S-2 2 example ! Draw the dot diagram of P and P-3 3