Unit 5: Electrons-lecture Regents Chemistry ’14-‘15 Mr. Murdoch Unit 5: Electrons 1. Student Name: _______________________________________ Class Period: ________ Page 1 of 61 Website upload 2014 Unit 5: Electrons-lecture Regents Chemistry ’14-‘15 Mr. Murdoch Page intentionally blank Page 2 of 61 Website upload 2014 Unit 5: Electrons-lecture Regents Chemistry ’14-‘15 Mr. Murdoch Unit 5 Vocabulary: 1. Anion: a negatively charged ion. 2. Cation: A positively charged ion. 3. Electron: A particle with a net charge of -1 and a mass 1/1836th of an amu located in the energy levels outside the nucleus. Electrons are lost, gained, or shared in the formation of a chemical bond. (e-) 4. Electronegativity: An atom’s attraction to electrons in a chemical bond. Electronegativity is used to determine bond types, polarity of a molecule, and attractive force type and strength. 5. Excited State: A condition where an atom’s electrons occupy higher energy levels than they normally would. 6. Frequency (ν) & (Hz): The number of wavelengths that pass a fixed point in one second. 7. Ground State: A condition where an atom’s electrons are occupying the lowest possible energy state. 8. Ion: A charged atom or molecule formed by the gain (or loss) of electrons. 9. Ionic Radius: The measure of the size of an ion. 10. Ionization Energy: The energy required to remove an atom’s most loosely held valence electron, measured when the element is in the gas phase. 11. Kernal: The atom beneath the valence electrons, including the rest of the electrons in the lower energy levels and the nucleus. 12. Orbital: A region of space around the nucleus that is the most likely location to find an electron in an atom. 13. Orbital Notation: Also known as “box diagrams”, these schematics describe the location and spin of the electrons in an atom. 14. Oxidation: The loss of electrons from an atom or ion. 15. Photon: An infinitesimally small particle that travels in a wave-like fashion after being released when electrons fall from the excited state to the ground state. A photon is also known as quanta. 16. Planck’s Constant (h): A proportionality constant that converts Hz (frequency) to Joules (energy). Planck’s Constant = 6.6 x 10-34 J/Hz 17. Reduction: The gain of electrons by an atom or ion. 18. Quantum: A four-digit series of numbers that identifies the location of a specific electron around the nucleus based on PEL, sublevel, orbital, and spin. 19. Shell (Principal Energy Level/PEL): The most probable location an electron may be found around the nucleus. Page 3 of 61 Website upload 2014 Unit 5: Electrons-lecture Regents Chemistry ’14-‘15 Mr. Murdoch 20. Stable Octet: An electron configuration that is reached when atoms gain, lose, or share electrons in an attempt to achieve a noble gas electron configuration of eight valence electrons. Hydrogen is an exception to this “Rule of Eight”. 21. Sublevel: The regions of space electrons occupy making up a principal energy level. 22. Speed of Light (c): The velocity (speed) of light photons in a vacuum, or 299,792,458 meters/second. 23. Valence electrons: The electrons that reside in the outermost principal energy level of an atom. These electrons are lost, gained, or shared in the formation (or decomposition) of a chemical bond. 24. Wavelength (λ): The distance from one crest to the next crest in a wave. Measured in meters. Page 4 of 61 Website upload 2014 Unit 5: Electrons-lecture Regents Chemistry ’14-‘15 Mr. Murdoch Unit 5 Homework Assignments: Assignment: Date: Due: Page 5 of 61 Website upload 2014 Unit 5: Electrons-lecture Regents Chemistry ’14-‘15 Mr. Murdoch Topic: An Overview of the Electron Objective: How did the electron come about to be understood? History of sub-atomic particle discovery: Watch History of Subatomic Particles video https://www.youtube.com/watch?v=kBgIMRV895w The Bohr model of the atom and electrons: Watch Bozeman Science The Bohr Atom video https://www.youtube.com/watch?v=GhAn8xZQ-d8 The Quantum-Mechanical Model of the atom: The current model of the atom has the atom containing a small, dense positively charged nucleus surrounded by electrons that travel in a wave-like motion around the nucleus. This motion is modified by mass and charge interactions between electrons and the nucleus. The interactions and the fast speed of the electron make it impossible to know both where an electron is and where it is going at any particular moment. All that can be known is a general area of probable space where the electron might be. Electrons travel in principal energy levels made up of sublevels, with each sublevel Page 6 of 61 Website upload 2014 Unit 5: Electrons-lecture Regents Chemistry ’14-‘15 Mr. Murdoch made up of orbitals that contain two electrons in each orbital. Electrons in the same orbital will spin in opposite directions. The end result is that the current model of the atom shows the electron’s around a nucleus closely resemble a cloud of gnats (the electrons) buzzing around your head (the nucleus). The Development of the Atom Model: Page 7 of 61 Website upload 2014 Unit 5: Electrons-lecture Regents Chemistry ’14-‘15 Mr. Murdoch Topic: Light Objective: Why does high temperature matter emit light? 1. Electrons (charge of -1 and having a mass of 1/1836th amu) surround the nucleus of an atom in distinct energy levels. Electrons (e-) occupy the lowest possible energy levels when the atom is in the ground state. 2. When electrons have energy added (in the form of light, heat, or electricity), electrons will rise in energy level by the same amount of energy that the electrons were given. The higher the energy added, the higher the electrons rise in level. The higher energy level is called the excited state. This is in accordance with the Law of Conservation of Energy, stating energy may not be created or destroyed by physical or chemical change. 3. As electrons are negatively charged, they are attracted to the positively charged nucleus, and will eventually release the excited state energy as they fall back to the ground state. 4. The energy released as an electron returns to the ground state is in the form of photons. Photons are the smallest known particles, and are essentially massless. Photons travel at the fastest theoretical Page 8 of 61 Website upload 2014 Unit 5: Electrons-lecture Regents Chemistry ’14-‘15 Mr. Murdoch speed possible, 3 x 108 m/sec, or the speed of light. Photons are considered particles of light. 5. The color of the light emitted is determined by the amount of energy released by the electron as it dropped back to the ground state. Light particles travel in a wave pattern. The more energy a photon has, the shorter its wavelength. Photons with wavelengths shorter than visible light (high energy) are found in gamma rays, X- rays, and ultraviolet. Visible light photons make up a very small part of the electromagnetic spectrum and are in the middle of the photon energy range. For visible light, the higher energy photons are violet, and the lower energy photons are red. Photons with wavelengths longer than visible light (lower energy) are infrared, radar, microwave, and radio. Page 9 of 61 Website upload 2014 Unit 5: Electrons-lecture Regents Chemistry ’14-‘15 Mr. Murdoch Topic: Light Objective: Why does high temperature matter emit light? 6. There are three properties of light waves: energy (Ɛ, in joules); wavelength (λ, in meters); and frequency (ν, in wavelengths per second, or Hz). Note that frequency, (ν), is the number of wavelengths that pass a given point in one second. All photons travel at the speed of light (3 x 108 m/sec), so all photons have the same speed. Therefore, a greater number of short wavelength photons will pass a certain point each second than will long wavelength photons. Watch Khan Academy Introduction to Light video https://www.youtube.com/watch?v=rLNM8zI4Q_M Page 10 of 61 Website upload 2014 Unit 5: Electrons-lecture Regents Chemistry ’14-‘15 Mr. Murdoch Topic: Electromagnetic Spectrum Objective: How do wavelength, frequency, and energy all relate? As the energy of a photon increases, the wavelength shortens and the frequency increases as more short wavelengths may pass a point in one second. The Continuous Electromagnetic Spectrum (from 2006 Physics Ref Table) Page 11 of 61 Website upload 2014 Unit 5: Electrons-lecture Regents Chemistry ’14-‘15 Mr. Murdoch Topic: Electron Energy levels Objective: What are the different drops of energy for electrons? Each atom has many electron levels. Electrons can drop from the excited state in different pathways. If an electron is excited from the first to the fourth energy level, the electron may fall back in one of the following pathways. i. From the 4th to the 1st energy level; ii. From the 4th to the 3rd to the 1st energy level; iii. From the 4th to the 2nd to the 1st energy level; iv. From the 4th to the 3rd to the 2nd to the 1st energy level. Each different drop in energy level emits light with a different amount of energy, and therefore a different wavelength (color). A sample of pure element subjected to electrical current excites the sample’s electrons. When the excited electrons fall back toward the ground state, the differing amounts of energy will give off different colors of light. The sample will look as if it glows a certain color. If the light emitted is projected through a prism onto a white backdrop, the individual energies of the emissions may be seen as bright lines (spectra) of different colors.