<p> Accelerated Chemistry Chapter 4 Notes – Arrangement of Electrons in Atoms Chapter 4 4.1 Refinements of the atomic model Models of the atom so far: Dalton – atoms are like little “bb’s” - then the ______gets discovered</p><p>Thomson – atom is like a ______“bb”</p><p>Rutherford - Gold foil experiment – ______“bb”</p><p>Bohr model of the atom (1913) – Neils Bohr – Danish Physicist</p><p>The Bohr model of the atom comes from the idea that light is ______</p><p>View vision learning example of hydrogen and helium atoms. http://web.visionlearning.com/custom/chemistry/animations/CHE1.2-an-atoms.shtml</p><p>The Bohr Atom (1913) In 1913, Neils Bohr, a Danish physicist proposed:  All the positive charge was in the ______</p><p> Electrons orbited the nucleus much like planets orbit the sun (at fixed distances)</p><p> The ______the electrons to the nucleus, the ______energy it has.</p><p> The ______the electron is from the nucleus, the ______energy it has.</p><p>09e61e140de58905d7904b2b3dc7c6bb.doc Page 1 of 13 Accelerated Chemistry Chapter 4 Notes – Arrangement of Electrons in Atoms</p><p>The Electromagnetic Spectrum - Defined  Visible light, x-rays, ultraviolet radiation, infrared radiation, microwaves and radio waves are all part of the electromagnetic spectrum </p><p> The spectrum consists of electromagnetic radiation – ______</p><p> Waves can be described by the wave equation which includes velocity (c = speed of light), wavelength (λ) and frequency (ν).</p><p> Wavelength (definition) = ______</p><p> Light through prism leads to high energy (violet) low energy (red)</p><p> ROYGBIV - colors of the visible spectrum</p><p> Bright Line Spectrum (BLS) – caused by e- emitting energy as they ______to ______energy level.</p><p> heat sodium - yellow light 2 colors</p><p> heat lithium - red light 4 colors</p><p> elements can appear to give off the same color light, but each will have its own bls</p><p> BLS - used to determine ______</p><p> BLS - validates Bohr’s idea that electrons jump to different energy levels and give off different wavelengths of light</p><p>09e61e140de58905d7904b2b3dc7c6bb.doc Page 2 of 13 Accelerated Chemistry Chapter 4 Notes – Arrangement of Electrons in Atoms</p><p>Light from the sun (white light) appears as a continuous spectrum of light. </p><p> Continuous Spectrum of Light (definition) = There are no discrete, individual wavelengths of light but rather all wavelengths appear, one after the other in a continuous fashion</p><p>Spectroscopy (definition) = ______</p><p>Show overhead #6 We will use spectroscopes (______) and flame tests to study elements because each element emits a different spectrum of light when exited .</p><p>Bohr proposed that the energy possessed by an e- in a H- atom and the radius of the orbit are quantized (bls)</p><p> Quantized (definition): a specific value (of energy)</p><p>The ramp is an example of a Like a set of stairs, the continuous situation in which energy states of an electron any energy state is possible up is quantized – i.e. electrons the ramp are only found on a specific step</p><p>Bohr’s Energy Absorption Process:</p><p></p><p> These energy levels are “ quantized “ (the e- cannot be in between levels), the e- disappears from one shell and reappears in another</p><p></p><p> Ground State Analogy = a spring and two balls</p><p>Both the atom and e- now This is an energy have higher energy emission process and The e- absorbs energy in the what we observe in the ground state and is excited hydrogen line spectrum to a higher level</p><p>“The Ground State” “The Excited State”</p><p>09e61e140de58905d7904b2b3dc7c6bb.doc Page 3 of 13 Accelerated Chemistry Chapter 4 Notes – Arrangement of Electrons in Atoms  When energy is added, the electron is found in the “______.”</p><p> The Excited State (definition) = ______</p><p> An illustration of Bohr’s Hydrogen atom (from ground to excited state):</p><p> The atomic line spectral lines - when an e- in an excited state decays back to the ground state</p><p>The electron loses energy, light (colors) is emitted and the e- returns to the ground state</p><p>09e61e140de58905d7904b2b3dc7c6bb.doc Page 4 of 13 Accelerated Chemistry Chapter 4 Notes – Arrangement of Electrons in Atoms</p><p>The Bohr Model - Summary</p><p>1. When an atom absorbs energy, its electrons are promoted to a higher energy level. When the electron drops back down, energy is given off in the form of ______. 2. Each distance fallen back is a specific energy, and therefore, a specific ______. 3. Since electrons can fall from level 5 to 4, 5 to 3, etc., ______Click for animated H-atom: Bohr's Atom: Quantum Behavior in Hydrogen - http://www.visionlearning.com/library/module_viewer.php? mid=51&l=15 </p><p>Bohr also predicted that since electrons would occupy specific energy levels and each level holds a specific number of electrons</p><p> The maximum capacity of the first (or innermost) electron shell is ______. </p><p> Any element with more than two e-, the extra e- reside in additional ______. </p><p>Group IA VIA VIIA VIIIA</p><p>Lithium Oxygen Fluorine Neon</p><p>Sodium</p><p>Electron Configurations for Selected Elements</p><p> The number of e- per shell = 2n2 (where n is then shell number)</p><p>09e61e140de58905d7904b2b3dc7c6bb.doc Page 5 of 13 Accelerated Chemistry Chapter 4 Notes – Arrangement of Electrons in Atoms</p><p>Draw Bohr Models for the elements with atomic numbers 1-10 below then abbreviate with nucleus and numbers on rings</p><p>09e61e140de58905d7904b2b3dc7c6bb.doc Page 6 of 13 Accelerated Chemistry Chapter 4 Notes – Arrangement of Electrons in Atoms</p><p>Short Hand Bohr Model  Write the symbol of the element  Use a ) to represent each shell  Write the # of e- in each shell</p><p>Element Short-Hand e- Configuration</p><p>Hydrogen H )1e- </p><p>Lithium Li )2e- )1e- </p><p>Fluorine F )2e- )7e- </p><p>Sodium Na )2e- )8e- )1e- </p><p>At atomic # 19 (z = 19), there is a a break in the pattern. One would expect that energy level #3 would continue to ______. However, the next two electrons go into the ______energy level. Look at K and Ca. </p><p>Bohr Model illustrations for elements 1-20 on the periodic table examples:</p><p>IA VIIIA H He</p><p>+ ) + ) IIA IIIA IVA VA VIA VIIA Li Be B C N O F Ne</p><p>+ ) ) + ) ) + ) ) + ) ) + ) ) + ) ) + ) ) + ) )</p><p>Na Mg Al Si P S Cl Ar</p><p>+ ) ) ) + ) ) ) + ) ) ) + ) ) ) + ) ) ) + ) ) ) + ) ) ) + ) ) )</p><p>K Ca</p><p>+ ) ) ) ) + ) ) ) )</p><p>So, there is a relationship between the main column # and the number of outershell electrons.</p><p>09e61e140de58905d7904b2b3dc7c6bb.doc Page 7 of 13 Accelerated Chemistry Chapter 4 Notes – Arrangement of Electrons in Atoms  Column # = the number of ______electrons</p><p>And, there is a relationship between the row # and the number of energy levels.  Row # = the number of ______</p><p>The Bohr model truly works well for the H atom only – for elements larger than H the model does not work.</p><p>In sum, Bohr made 2 huge contributions to the development of modern atom theory  He explained the atomic line spectra in terms of ______</p><p> He introduced the idea of quantized electron ______in the atom</p><p>The Bohr atom lasted for about 13 years and was quickly replaced by the quantum mechanical model of the atom. The Bohr model is a good starting point for understanding the quantum mechanical model of the atom Do Ch4 worksheet #1 – question #1</p><p>4.2 Quantum numbers and atomic orbitals & 4.3 Electron Configuration The Bohr model describes the atom as having definite orbitals occupied by ______. As with all chemistry, we soon learn that the Bohr model is a lie.</p><p>Schrödinger (1926) introduced wave mechanics to describe electrons  Based his idea that electrons behaved like ______</p><p> Electrons show diffraction (interference) properties like ______.</p><p> Treats electrons as waves that are found in ______.</p><p> Orbitals (definition) = ______.</p><p>So, the Bohr model really is ______</p><p>There are really many types of orbitals – we can see them on the periodic table</p><p>09e61e140de58905d7904b2b3dc7c6bb.doc Page 8 of 13 Accelerated Chemistry Chapter 4 Notes – Arrangement of Electrons in Atoms</p><p>Draw spdf blocks on blank periodic table</p><p>Subatomic Orbitals Type # of Sublevels Total # electrons Shape S Sphere p Peanut d Dumbbell f Flower</p><p>Quantum Numbers</p><p>Quantum numbers show the “addresses” of electrons – each electron has 4 different quantum numbers:</p><p>1. principle (n): ______</p><p>2. azimuthal (l): ______</p><p>3. magnetic – ______</p><p>4. spin - ______</p><p>09e61e140de58905d7904b2b3dc7c6bb.doc Page 9 of 13 Accelerated Chemistry Chapter 4 Notes – Arrangement of Electrons in Atoms Electron Configuration - a representation of the arrangement of electrons in an atom </p><p> Examples of electron Configuration</p><p> 1. Li 1s22s1</p><p> 2. C 1s22s22p6</p><p>-Take note that after 4s is filled, 3d is than filled before 4p. This is because 4s has a lower energy than 3d.</p><p>-…… 6s than 4f than 5d than 6p</p><p>-When writing out the electron configuration, always write your numbers in numerical order </p><p> Y 1s22s22p63s23p64s23d104p65s24d1 – NO!</p><p> Y 1s22s22p63s23p63d104s24p64d15s2</p><p>- Note: 3d has a few exceptions exceptions o Cr is 4s1 3d5 and Cu is 4s1 3d10 - students should be able to identify these elements simply based on how many electrons they have.</p><p>Examples: Be O</p><p>Ca Mn</p><p>Pb Os</p><p>09e61e140de58905d7904b2b3dc7c6bb.doc Page 10 of 13 Accelerated Chemistry Chapter 4 Notes – Arrangement of Electrons in Atoms We can also do shorthand electron configuration. Use previous row’s noble gas in brackets, then present the electron configuration for the current row.</p><p>Be Na Si</p><p>Orbital notation is another way to represent electron arrangement in atoms.</p><p>Electrons enter orbitals in a set pattern. For the most part, they follow these rules:</p><p>1. The Aufbau Principle - electrons must fill lower energy levels before entering ______.</p><p>Draw energy level diagram here: Draw diagonal diagram here:</p><p>Orbitals are like "rooms" within which electrons "reside". The s subshell has one s-orbital. The p subshell has three p-orbitals.</p><p>Each orbital can hold at most 2 electrons</p><p>See a good online illustration at http://www.avogadro.co.uk/light/aufbau/aufbau.htm 2. Hund’s Rule (better known as the ______) Before any second electron can be placed in a sub level, all the orbitals of that sub level must contain at least one electron – spread out the e- before pairing them up.</p><p>09e61e140de58905d7904b2b3dc7c6bb.doc Page 11 of 13 Accelerated Chemistry Chapter 4 Notes – Arrangement of Electrons in Atoms</p><p>3. Pauli Exclusion Principle - electrons occupying the same orbital ______. Examples: Li F</p><p>Na Sc</p><p>We can also do shorthand orbital notation (outer shell only)</p><p>Ca N Fe</p><p>Significance of electron configurations</p><p>Valence shell electrons - ______</p><p> no atom has more than ______</p><p>Noble gases - 8 valence electrons - ______reactive of all elements</p><p>Lewis Dot structures: NSEW (cheating) also show correct way, count to 8</p><p>Lewis Dot Structures</p><p>Exception – He</p><p>Try Lewis Dot structures for additional elements here:</p><p>09e61e140de58905d7904b2b3dc7c6bb.doc Page 12 of 13 Accelerated Chemistry Chapter 4 Notes – Arrangement of Electrons in Atoms</p><p>09e61e140de58905d7904b2b3dc7c6bb.doc Page 13 of 13</p>