Transcript Chapter 10
Chapter 10 The “non-history” parts of this chapter Electromagnetic Radiation 10.2 Electromagnetic radiation – light EM spectrum song Remember these from CPE? What important info are the pictures trying to say? • In these illustrations what does light look like? • With reference to the entire electromagnetic spectrum, how big is the portion we can “see”? • Which waves have the most energy? • How do you know? Now that we know the visible light spectrum is only a small part of the entire electromagnetic spectrum, lets examine visible light closer. How are wavelengths measured? Look at the wavelengths of light. How does the size of a red wave of light compare in size to a blue wave of light? Which wavelength of visible light has the most energy? (don’t know??? Look back at the last slide and compare the color location with reference to the rest of the spectrum and what you know about the energy levels of gamma vs microwaves) The Nature of light • http://www.youtube.com/watch?v=Puzw9TDo9s&safe=active • When you view this video think about the following questions? ▫ What does it mean when scientists say light comes in different frequencies? ▫ Which waves are considered light waves? ▫ How/what can emit light? ▫ How are element’s emission spectrum like a fingerprint? Light is a wave? • https://www.youtube.com/watch?v=zuYMV-SfGg ▫ Watch this video and think about the ollwoing questions How is a light wave a disturbance is a medium like a water wave is a disturbance in water? Can light waves exist as different frequencies? Light is a particle? • http://www.youtube.com/watch?v=kJBcXFsFa7 Y&safety_mode=true&safe=active&persist_safet y_mode=1 • Watch this video and think about the following queations ▫ What two scientists paved the way for our current understanding of light? ▫ What evidence supports light as a wave? Double what????? • Watch the following video to see what new information we found out about light through experimentation • https://www.youtube.com/watch?v=fwXQjRBL wsQ ▫ Can you describe in your own words what happened in this experiment? ▫ What was the concluding results of this experiment? Light as a particle????? • In previous years we have studied light as a wave (like the pictures we looked at) • Thus we visualized electromagnetic radiation (light) as a wave that carries energy through space • But in chemistry class we will also study light as a particle (called a photon) A photon is a quantum packet of energy. ▫ Which is correct way to envision light? BOTH!! Light behaves as both a wave and a particle • FYI- just like a blue wavelength carries more energy, a blue photon of light also carries more then a red one Emission Of Energy by Atoms 10.3 & 10.4 • Watch the following video: http://www.youtube.com/watch?v=kJBcXFsFa7Y&safety_mode=true&safe=active&persist_safety_mode=1 • Think about these questions ▫ What does mean when scientists say that an electron is “excited”? ▫ What is emitted when a electron moves from a lower energy level to a higher one? ▫ What is emitted? ▫ What is a photon? ▫ How does an electron move to a higher energy level? ▫ What is another term for an energy level of an atom? ▫ Why do different elements emit different spectrums of light? Quantum Nature of Light • Read the book pages 286-287 • As you read think about the following questions: ▫ What is the quantum nature of light? ▫ What does it mean by light exists on stair steps? Quantum Nature of Light Need more explanation? Watch this video: https://www.youtube.com/watch?v=EzHeTe14qS U STOP The Hydrogen Orbitals https://www.youtube.com/wa tch?v=K-jNgq16jEY 4th energy level 3rd energy level 2nd energy level 1st energy level 10.7 https://www.youtube.com/wa tch?v=VfBcfYR1VQo The Hydrogen Orbitals Don't forget each parallelogram can break into separate more sublevels 2s 2p 2p 2p FYI • As principle energy levels increase so does the size of the orbital 3s 1s 2s • Refer to 3D models STOP Orbital Diagrams http://www.youtube.com/watch?v=5N6JYY_QDw8 Old Stuff to Apply • Maximum number of electrons per orbital • s = 2 (1 orbital) • p = 6 (3 spacial variations of the p orbitals x,y,z) • d = 10 (5 spacial variations of the d orbitals yz, xz,xy, x2 – y2, z2 ) • f = 14 (7 spacial variations of the f orbitals) New stuff to Understand • • • • • • 1s 2s, 3s, 4s, 5s, 6s, 2p 3p, 4p, 5p, 6p, 3d 4d, 4f 5d, 5f 6d, 6f Spin Property 10.8&10.9 • Property that determines how electrons can be arranged in an atom • Electrons appear to be spinning like a top on its axis • Each electron only spins in one direction and there are only two possible directions to spin ▫ We represent the spin with arrows • What is most important: ▫ PAULI EXCLUSION PRINCIPLE Orbital can hold a max of two electrons and those two electrons must have opposite spins to inhabit the same orbital Other rules for orbital diagrams… Aufbau Principle Hund’s Rule • Orbitals of lowest energy are filled first. • Every orbital within an energy level will have one electron before any orbital has two electrons Example: 1s will have 2 electrons before you move to the 2s level Practice: • • • • Ground state for the following: Br First figure out how many electrons Br has. Then: __, __, etc….. 1s 2s Practice: • Ground state for the following: Br • __, 1s __, 2s __,__,__, __, 2p 3s __,__,__, 3p __,__,__,__,__, __,__,__, 3d 4p Write as: 1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p5 Homework: Electron Configuration Practice #1 __, 4s Easier way to figure electron configuration 10.9 The “exponent” number is determined by how many spaces over the element is Exceptions: Cu = 4s1, 3d10 and Cr = 4s1, 3d5 STOP Electron Configuration Short Hand • Use noble gas/abbreviated e config in the electron configuration notation • Use the previous noble gas Example: Na Ne 3s1 Example : Ge Ar 4s2, 4d10, 4p2 HW: p311( 57, 58, 59-68evens) STOP Atomic Properties • Metallic property • Ionization Energy • Atomic Size Metallic property – how likely is the element to want to lose a metal? Atomic Radius – size of atom Overall: atomic size • Atomic size INCREASES going down a row……makes sense more electrons = bigger radius • But atomic size DECREASES going across a period WHY? • Expect atoms to be same size since they are all in same energy level, however as we move across the period there are also more protons. • This resulting increase in positive charge causes on the nucleus tends to pull the electrons closer thus DECREASING the over size of the radius Ionization Energy – energy required to remove an electron what do you notice about the chart? Ionization Energy – energy required to remove an electron what do you notice about the chart? Overall: Ionization Energy • As you move across a period, the Ionization Energy increases (Why?) • Nonmetal do not want • to loose their electrons • Therefore ionization energy increases across a period Overall: ionization energy • As you move Down a Group, the Ionization Energy Decreases (Why?) • - An increase in the Atomic Radius (causes a Decrease in Ionization Energy) • - More electrons, Shield the Outer Electrons from the charge associated with the nucleus. This shielding interferes with the protons' ability to pull on the valence electrons thus causing the atoms with many core electrons to have a larger atomic radius. Summary of trends Homework: p312 (69-78 and 80, 82)