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Name_______________________________ Chemistry Atomic Structure Essential Question: How was the structure of the atom determined? Vocabulary: bright-line spectrum electron configuration excited state ground state orbital wave-mechanical model Part 3: Wave-Mechanical Model of the Atom Key Question: How does the wave mechanical model explain the location of electrons? 1. Dalton’s Atomic Theory (1803): 1. ______________________________________________________________________________ 2. ______________________________________________________________________________ 3. ______________________________________________________________________________ 4. ______________________________________________________________________________ 2. Modifications to Dalton’s Theory: JJ Thomson (1897);___________ _______________ model based on his discovery of the electron Ernest Rutherford (1911): 1. Atom is mostly __________ __________ 2. At center of atom is a dense positively charged __________________ 3. Niels Bohr and other physicists studied light given off by elements with a ____________________ Why were they studying light? They could apply principles about the nature of light to the nature of subatomic particles. What is light? 1. Newton (1600’s): light travels through space as a ___________________ 2. Maxwell (1864): light travels through space as a beam of ________________ 4. Electromagnetic Spectrum: (wavelengths in meters) 10-12 10-10 10-8 4 to 7 x10-7 Gamma X rays UV Visible light 10-4 IR 10-2 Micro Wavelength increases Frequency decreases Energy decreases Speed is constant = 3.00 X 108 m/sec 1 102 Radio waves FM short AM 104 5. Properties of Electromagnetic Waves: Wavelength ( ): distance between two ____________ in a wave Frequency: ____________ of waves that pass a given point per second Speed: measured in __________ per second (3.00 x 108 m/s) 6. Bohr: From his observations about light given off by elements Knew that the color of light emitted by a star or element indicated how much ____________ was being released. Thought that as an atom gained energy from heat, electricity, etc., that it was the ______________ that gained the energy. Electrons normally in the ____________ ____________, close to the nucleus Electrons become ____________ when energy is added and they move away from the nucleus Excited state is ____________: electrons return to the ground state releasing energy as ____________, ____________, ____________ Bright-line ____________ shows energy released from the electrons as they return to the ground state 7. Bohr Experiment with the Bright-line Spectrum of Hydrogen Line Spectra and the Energy Level Diagram 1. In this activity we will investigate the spectrum of hydrogen just as Niels Bohr did in 1913. Remember that energy may be added to electrons in the form of heat, light, or electricity. As this energy is added, the electrons are promoted to higher, or excited, energy states. As the electrons lose this energy, light is emitted. The wavelengths of the light emitted enable us to determine the energy levels that the electrons occupied. 2. This emitted light may be measured using a spectroscope or diffraction film. From the wavelength, the ENERGY associated with each color may be determined using the following formula: EKJ = 119,557 This equation comes from work done by Max Planck and Louis de Broglie who were investigating the wave-like properties of matter. Energy is measured in kilojoules. 3. Your teacher will place a tube filled with hydrogen gas in a high voltage apparatus. As electricity flows through the hydrogen, observe the spectrum seen using the diffraction film in the glasses. For each color observed, record both the color and the wavelength in the table below. The wavelength Using the equation above, calculate the energy values and record in the table. Approximate Color Wavelength Energy (kilojoules) 4. The energy transitions you have seen occurred when the electrons fell back to the second energy level. Transitions back to the first level were not seen since they are in the ultraviolet region. 5. Use these values to construct the energy level diagram for hydrogen on the back of this page. For this diagram you will need to know at what energy the highest energy level is located. This can be found by using Table S to look up the first ionization energy for hydrogen. This energy is the amount of energy needed to strip an electron from the atom of hydrogen and therefore corresponds to the highest possible energy level. First Ionization energy for hydrogen: __________ 6. After completing the plotting of the energies you observed, draw arrows to correspond to the electrons returning to the second energy level. 1500E N E R G Y (kJ/ mol) 1000- 500- 7. Questions to answer: ________________ a. Which color of light contains the greatest amount of energy? ________________ b. The least amount of energy? ________________ c. To which energy level did all the excited electrons return to? ________________ d. An electron absorbs a specific amount of energy, called a ___, when it jumps to a higher energy level. ________________ e. Each color represents a specific amount of energy released by an electron and is called a___. ________________ f. Each line on the diagram represents a different ___ level in the hydrogen atom. Bohr Model of the Atom 1. Parts of Bohr’s model: 1.) Electrons orbit the nucleus in __________ orbits at fixed distance called __________ __________ 2.) Electrons farther from the nucleus contain (more, less) energy 3.) When electrons gain energy, they move from the _________ __________ to higher energy levels 4.) Electrons return to the ground state by releasing energy in specific amounts called ____________ 2. Problems with the Bohr Model 1.) It did not account for all the __________ in the spectra of the other elements. 2.) With better instruments, the model did not even work for ___________. 3. Heisenberg Uncertainty Principle (1927): it is not possible to know the exact __________ and ____________ of a subatomic particle. 4. Wave Mechanical or Quantum Model: based on the _________________ of finding an electron in a given region of space around the nucleus. Proposed by Erwin Schrodinger and Louis DeBroglie and uses Bohr’s __________ __________ as distances from the nucleus. 1.) Electrons do not move in __________ paths around the nucleus. 2.) Electrons farther from the nucleus have ________ energy. 3.) An ____________ is a region in space with a high probability of finding an electron. 5. Demonstration- Penny Toss! Wave Mechanical, or Quantum, Model of the Atom 1. Principal Energy Level (Bohr) = Principal Quantum Number, n I N C R E A S I N G n=4 n=3 n=2 E N E R G Y n=1 2. Energy Sublevels: found within the Principal Energy Level (account for the extra lines in the spectra of other elements) 1.) Number of Sublevels = Principal Quantum Number, n n = 1, _____ sublevel n = 2, _____ sublevels n = 3, _____ sublevels 2.) Energy of each sublevel is slightly _______________. 3.) Each electron in a given sublevel has _______________ amount of energy. 4.) Sublevel symbols are s, p, d, f Draw the sublevels in the diagram above. 3. Orbitals: regions with a sublevel where electrons may be found 1.) Each orbital can hold _____ or _____ electrons. 2.) Number of orbitals in each sublevel s sublevel = _____ orbital p sublevel = _____ orbitals d sublevel = _____ orbitals f sublevel = _____ orbitals 3.) Number of orbitals in a Principal Energy Level = n2. Use draw the orbitals in an energy level. on the diagram on the front to 4. Electron Spin: electron rotates on its axis like the ____________ 1.) Opposite spins: ____________ and ____________ 2.) Pauli Exclusion Principle: only _____ electrons can occupy the same orbital, each with opposite spin 5. Shapes of Orbitals: 1.) s orbital: ____________ shape; higher Principal Energy Levels has __________ diameter. See p. 131 in textbook. Diagram below. 2.) p orbital: ____________ shape around the nucleus and each axis. Diagram below. 6. Hund Rule: must place 1 electron in each p orbital before a second electron can go in. Think of the Birthday Rule!! 7. Fill in orbital structures for the atoms below. Use these three rules: Aufbau principle: electrons occupy the orbitals of ____________ energy first. Pauli exclusion principle: an atomic orbital may describe at most _____ electrons. Hund’s rule: one electron enters each orbital until all orbitals contain one electron with _____ spin Element Atomic Number 1s 2s 2p 3s 3p 4s H _____ Li _____ B _____ C _____ O _____ F _____ Ne _____ Na _____ Al _____ S _____ Ar _____ K _____ Ca _____ 8. Summary of Wave Mechanical Model Principal Quantum Number n Number of Orbitals n2 Sublevel s p d f Number of Electrons 2n2 9. Electron Configurations: shorthand method for showing electron location in an atom. Write the electron configurations for the atoms listed in #7 on the previous page. H ___________________________________________________________________________ Li ___________________________________________________________________________ B ___________________________________________________________________________ C ___________________________________________________________________________ O ___________________________________________________________________________ F ___________________________________________________________________________ Ne ___________________________________________________________________________ Na ___________________________________________________________________________ Al ___________________________________________________________________________ S ___________________________________________________________________________ Ar ___________________________________________________________________________ K ___________________________________________________________________________ Ca ___________________________________________________________________________ 10. Write the electron configuration for an atom of copper. Cu ___________________________________________________________________________ Look at the Periodic Table. What does it give for copper’s electron configuration? ___________ Orbital Notation Practice and Questions 1. Complete the orbital notation for the elements below. Atomic Number 1s 2s 2p 3s 3p 3d 4s 4p H _____ Li _____ Ne _____ Si _____ Fe _____ Br _____ 1st 2nd 3rd Principal Energy Levels 2. Complete the following table (Note PQL = Principal Quantum Level, n) Atomic Number H=___ Li=___ Ne=___ Si=___ Number of Electrons Number Occupied Orbitals Number Filled Orbitals Number of Unpaired Electrons Number of Electron Pairs Number of Occupied Sublevels Number of Filled Sublevels Number of Occupied PQL’s Number of Filled PQL’s PQL of Highest Occupied PQL Number of Valence Electrons (outermost energy level) Number of Kernel Electrons (non-valence electrons) Number of Unpaired Valence Electrons 4th Fe=___ Br=___ Significance of Wave Mechanical Model 1. Periodic Table Relationships 1.) Period (row) corresponds to the ____________ ____________ Level being filled with electrons example: For Period 3, which Principal Energy Level is filling?_____ 2.) Electron configurations given in block for each element in _______________ corner. You need to know the filling order!! 3.) Blocks of elements correspond to the sublevel being filled s block: Groups _____ and _____ filling p block: Groups _____, _____, _____, _____, _____, _____ filling d block: Groups _____ through _____ filling (includes the ____________ elements) f block: _______________ and _______________ Series filling 2. Belated filling: when an ____ sublevel fills before a lower p sublevel. Example: 4s fills before the _____ 3. Valence Electrons: electrons in the _______________ Principal Energy Level for an element Valence Shell: corresponds to the __________; determines the __________ properties of an atom Filled Valence Shell: Group _____ elements called the __________ or __________ Gases 8 electrons in valence shell indicates chemical _______________. Group: elements in the same vertical column with the __________ number of valence electrons 4. Kernel: nucleus and all _______________ electrons. 5. Excited State Configurations: look for electrons not in lowest possible energy levels Atomic Ground State Excited State Number oxygen _____ 1s2 2s2 2p4 1s2 2s2 2p3 3s1 2-6 6. Ions: atoms with __________ or _________ electrons Atomic Ground State Number oxygen _____ 1s2 2s2 2p4 2-6 __________ Ion 1s2 2s2 2p6 __________