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Date Created: 09/20/15
CHEMISTRY 1010 NOTES WEEK ONE September 14 September 18 2015 Courtney Burke 707 266 4834 SECTION 11 States of Matter 0 Chemistry The study of matter and its properties the changes that matter undergoes and the energy associated with the changes 0 Matter Anything that has mass and volume 0 Composition of Matter The types and amount of simpler substances that make up matter 0 Matter occurs in three physical forms called states 0 Solid Has a fixed shape does not conform to its container atomic particles lie next to each other in a regular three dimensional array 0 Liquid Has a varying shape conforms to the container shape but only to the extent of the liquid s volume atomic particles lie close together but move randomly amongst each other 0 Gas Has a varying shape conforms to the container shape and fills the entire container does not have a surface atomic particles have large distances between them and move randomly throughout the container The Properties of Matter 0 Properties The characteristics that give each substance its unique identity 0 Physical Properties Characteristics a substance shows by itself without interacting with another substance ex melting point electrical conductivity density 0 Ex Water solid state I Water liquid state 0 A physical change occurs when a substance alters its physical properties not composition 0 Chemical Properties Characteristics a substance shows as it changes into or interacts with another substance 0 A physical change caused by heating can be reversed by cooling This is not true for a chemical change 0 The distinction between chemical and physical change is defined by composition Importance 0fEner2v in the Study of Matter 0 Energy The ability to do work 0 The total energy an object possesses is the sum of its potential energy and its kinetic energy 0 Potential Energy The energy due to the position of the object relative to other objects 0 Kinetic Energy The energy due to the motion of the object 0 When energy is converted from one form to another it is conserved not destroyed 0 Situations of lower energy are favored over situations of higher energy 0 Electrostatic forces interactions like charges repel each other and opposites attract 0 The chemical potential energy of a substance results from the relative positions and the attractions and repulsions among its particles SECTION 71 The Wave Nature ofLith 0 The wave properties of electromagnetic radiation are described by three variables and one constant 0 Frequency The number of complete waves or cycles per second Measured in Hertz Hz 0 Wavelength The distance the wave travels in one cycle 0 Speed The speed of a wave is the distance it moves per unit of time meters per second gt Speed of light c v X A O Amplitude Height of the wave crest related to the intensity of the radiation or its brightness 0 Electromagnetic Spectrum f 7 Increasing energyr r Inereeeing wevelengl h 391 l rum l nm quotEU nm l nm l em I l m lEl m 39 7 I I n n n Gamma mes Xenanee Ulilire Infrared Eadie weavesquot wiele r Radar FM 7 eiaiblelighr I I1 I 43930 em 518039 nm EDIE nm Fl ram 0 Light of a single wavelength is called monochromatic light of many wavelengths is called polychromatic The Classical Distinction Between Energy and Matter 0 Refraction When a light wave strikes the boundary between two media ex air and water at an angle other than 90 the change in speed causes a change in direction causing the wave to continue at a different angle 0 Dispersion When white light enters through a prism it is separated into its component colors because each incoming wave is refracted at a different angle 0 Diffraction When a light wave bends around an object it bends around both edges of the slit and forms a semicircular wave on the other side of the opening 0 Interference constructive and destructive The interaction of emerging circular waves due to waves of light passing through two adjacent slits When the amplitudes are added together in phase to form a brighter region the interference is constructive When the crests coincide with the troughs out of phase the interference is destructive The Particle Nature ofLith 0 The Quantum Theory Each change in an atom s energy occurs when the atom absorbs or emits one or more packets or definite amounts of energy 0 MaX Planck developed a formula to fit this phenomenon AB hv h 662606874 X 103934 joulessecond De Broglie s Equation h mv it a wavelength i n meters v the val eel ty in meterssee m a the maaa it a kilograms h 2 Fl amka s conetantt in MHZ Where SECTION 72 Line Spectra and the RydbergJ Eauation 0 Line Spectrum When light from electrically excited gaseous atoms passes through a slit and is refracted by a prism it creates a series of fine lines at specific frequencies separated by black spaces 0 Rydberg s equation predicts the position and wavelength of any line in a given series R 6626 X 103934 The Bohr Model of the Hydrogen Atom 0 The H atom has only certain energy levels called stationary states Each state I associated with a fixed circular orbit of the electron around the nucleus The higher the energy level the farther the orbit is from the nucleus 0 The atom does not radiate energy while in one of its stationary states 0 The atom changes to another stationary state only by absorbing or emitting a photon Ephoton AEatom E nal Emma hV 0 The quantum number n is a positive integer l 2 3 O The lower the 11 value the smaller the radius of the orbit and the lower the energy level 0 When the electron is in the first orbit n 1 it is closest to the nucleus and in it s lowest energy level called the ground state 0 If the electron is in any orbit farther from the nucleus the atom is in an excited state 0 If an H atom absorbs a photon whose energy equals the difference between lower and higher energy levels the electron moves to the outer orbit 0 If an H atom in a higher energy level returns to a lower energy level the atom emits a photon whose energy equals the difference between two levels 0 Since an atom s energy is not continuous but rather has certain states an atomic spectrum is not continuous 0 The Bohr model failed to predict the spectrum of any other atom because 0 It is a one electron model 0 Electrons do not have defined fixed orbits O The energy of an atom occurs in discrete levels and it changes when the atom absorbs or emits a photon of specific energy The Energy Levels of the Hvdrozen Atom 0 Finding the difference between two energy levels AB Efinal Emma 218 X 1018 J 1112 na1 1n2initial SECTION 73 The Wave Nature of Electrons and the Particle Nature of Photons 0 Matter and energy are alternate forms of the same entity 0 If energy is particle like matter is wave like 0 deBroglie Wavelength Matter behaves as though it moves in a wave h h A 1 my 0 Results on the atomic scale show electrons moving in waves and photons having momentum Both matter and energy show both behaviors O This dual character of matter and energy is known as the waveparticle duality Uncertainty Principle It is impossible to know simultaneously the position and momentum of a particle Air ip 4 m Unee ainty of Position p Unce ainty of hinmentum SECTION 74 The Atomic Orbital and the Probable Location of the Electron Quantum Mechanics Examines the wave nature of objects on an atomic scale Schrodinger Equation W is called a wave function a mathematical representation of the electrons matter wave in three dimensions The H symbol is called the Hamiltonian operator representing a set of mathematical operations that when carried out with a particular W yields one of the allowed energy states HWfEW W2 is called the probability density a measure of the probability of finding an electron in some tiny volume of the atom Electron Density Diagram The value for W2 for a given volume is shown with dots the greater the density of the dots the higher the probability of finding an electron in that volume The electron probability density decreases with distance from the nucleus Radial Probability Distribution Plot The volume of each layer increases faster than its density of dots decreases Probability Contour We cannot assign a definite volume to an atom Therefore we must use the probability contour eX an atom with a 90 probability contour means the electron is somewhere within that volume 90 of the time Oaantam Numbers of an Atomic Orbital Principle Quantum Number 11 a positive integer 1 2 3 and so forth 0 Indicates the relative size of the orbital and the relative distance from the nucleus 0 The higher the 11 value the higher the energy level Angular Momentum Quantum Number 1 is an integer from O to n 1 0 Related to orbital shape 0 N1 Ill01 value N 2 I l O 1 two values N 3 I l O 1 2 3 three values Magnetic Quantum Number m1 is an integer from 1 through 0 to 1 OOOO Prescribes the three dimensional orientation of the orbital in space around the nucleus An orbital with l O can only have m 0 An orbital with 1 1 can have m1 1 0 1 The number of m values 21 1 the number of orbitals given for l The total number of m values for a given 11 value n2 the total number of orbitals in that energy level Quantum Numbers and Energy Levels 0 The atom s energy levels shells are given by the 11 value 0 The atom s levels are divided into sublevels that are given by the 1 value L O is an s sublevel L 1 is a p sublevel L 2 is a d sublevel L 3 is an f sublevel 0 Orbitals n l Sublevel Name Possible m1 Values of Orbitals 3 2 3d 2 1 0 1 2 5 2 0 2s 0 1 5 1 5p 1 0 1 3 4 3 4f 3 2 1 0 1 2 3 7 Shapes of Atomic Orbitals 0 The s Orbital l O has a spherical shape with the nucleus at it s center 0 O O The 1s orbital holds the electron in the H atom s ground state The electron probability is highest at the nucleus The 2s orbital has two regions of higher electron density The radial probability distribution is higher than that of the closer one because the sum of W2 for it is taken over a much larger volume Between the two regions is a spherical node The 3s orbital has three regions of high electron density and two nodes The highest radial probability is at the greatest distance from the nucleus 0 The p Orbital An orbital with an 1 lis a p orbital O O O 0 Two regions of high probability one on either side of the nucleus The nucleus lies at the nodal plane of this dumbbell shaped orbital The maXimum value of l is n 1 only levels with n 2 or higher have a p orbital p orbitals have different spatial orientations three possible m values of 1 0 1 0 The d Orbital An orbital with l 2 is called a d orbital O O 0 M1 values for l 2 are 2 1 0 1 2 Two mutually perpendicular nodal planes between them and the nucleus at the junction of the lobes A d orbital must have a principal quantum number of n 3 or higher so 3d is the lowest energy d sublevel 0 Orbitals with l 3 are f orbitals and have a principal quantum number of at least 11 4 0 Each f orbital has a complex multi lobed shape with several nodal planes SECTION 81 The ElectronSpin Ouantum Number 0 Spin Quantum Number ms has two possible values l2 or l2 0 Each electron in an atom is described by a et of four quantum numbers the first three describe its orbital and the fourth describes its spin The Exclusion Principle 0 No two electrons in the same atom can have the same four quantum numbers 0 An atomic orbital can hold a maximum of two electrons which must have opposing spins Electrostatic Effects and EnergyLevel SplittingJ 0 The energy of an orbital in a many electron atom depends mostly on its 11 value size and to a lesser extent on its 1 value shape 0 This energy difference arises from three factors nuclear attraction electron repulsions and orbital shape 0 Their interplay lead to two phenomena shielding and penetration which occur in all atoms except hydrogen 0 A higher nuclear charge increases nucleus electron attractions and thus lowers sublevel energy stabilizes atom 0 Repulsions counteract the nuclear attraction by making the electron easier to remove 0 Shielding Reduces the full nuclear charge to an effective nuclear charge zeff the nuclear charge an electron actually experiences and this lower nuclear charge makes it easier for an electron to be removed 0 Penetration 0 Increases the nuclear attraction O Decreases shielding 0 Order of sublevel energies SltPltDltF
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