Chem 2030 Notes (Chapter 1)
Chem 2030 Notes (Chapter 1) CHEM 2030 - 01
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CHEM 2030 - 01
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This 9 page Class Notes was uploaded by Shannon Z. on Thursday September 3, 2015. The Class Notes belongs to CHEM 2030 - 01 at University of Missouri - Columbia taught by Rainer Glaser in Fall 2015. Since its upload, it has received 172 views. For similar materials see Survey of Organic Chemistry in Chemistry at University of Missouri - Columbia.
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Date Created: 09/03/15
Chemistry 2030 Dr Glaser Chapter 1 1 Structure of Atoms a Kernel contains the nucleus and filled electron shells i Nucleus 1 Contains protons and neutrons a Protons positively charged b Neutrons neutral charge i Hydrogen has no neutrons but rather a single proton 2 Source of most of the atom s weight ii Filled electron shells 1 No valance electrons b Electrons i Negatively charged ii Orbit around the nucleus in shells and orbitals 1 Orbitals a Can contain a maximum of two electrons b Differ in shape c Represented by the letters s p and d i There is one s orbital ii There are three p orbitals iii There are 5 d orbitals d Electrons in the same orbital spin in different directions i An arrow is used to show the direction an electron is spinning in e Grouped into shells 2 Shells a Shells are groups of orbitals b Represented by numbers 1 2 3 c The shell s number tells us how many types of orbitals it contains i Shell one contains one type of orbital 1s ii Shell two contains two types of orbitals 2s and 2p d A filled shell is one that holds the maximum amount of electrons i Filled shells don t participate in chemical bonding Valance electrons do iii Valance electrons 1 Electrons in the outermost unfilled shell c Atomic number i The number of protons in the nucleus ii Ex Beryllium s atomic number is 4 d Atomic Weight I An approximate number that represents the combined numbers of protons and neutrons in a nucleus ii Electrons are not included in this count because they are very light iii Ex The atomic weight of Beryllium is 9012 2 Charges a Neutral Atom i A neutral atom exists when the positive charge of the protons in the nucleus is balanced out by the electrons orbiting the nucleus 1 Balanced charge same number of protons and electrons ii For neutral atoms the atomic number not only represents the number of protons in the nucleus but also the number of electrons around the nucleus b Proton i Positivelycharge c Neutron i Neutral charge d Electron i Negative charge 3 Lewis Dot Structure text table 13 a A simple way of representing an atom s valance structure b Consists of the elemental symbol and dots representing each of the valance electrons i Example Carbon ii Element symbol also represents the kernel I a 1 C for carbon i iii Carbon has four valance electrons Each dot represents one valance electron 1 Note how the dots are spread around the different sides of the elemental symbol This is supposed to represent an electron s tendency to repulse each other 4 Molecular Formula a The molecular Formula tells the numbers of different atoms present b Example water i Molecular Formula H20 ii The H2 tells us that there are two Hydrogen atoms iii The O tells us that there is one Oxygen atom 5 Chemical bonds a Atoms combine or bond to become more stable Atoms that are already stable like inert gasses do not need to combine with other atoms i Stable atom eight valance electrons with the exception of hydrogen which needs two valance electrons ii Having eight electrons is called having a full octet b Atoms can bind to one another to become more stable in two different ways i Ionic bond 1 Occurs when one atom gives it s electrons to another atom 2 The atom that gains the electron becomes negatively charged because it gained the negative charge of the electron and is called an anion 3 Atoms that tend to accept electrons are called electronegative a On the periodic table the more electronegative elements are on the top or towards the right 4 The atom that loses the electron becomes positively charged because it lost the negative charge of the electron and is called a cation 5 Atoms that tend to give up their electrons are called electropositive a On the periodic table the more electropositive elements are on the bottom or towards the left 6 Example of an ionic bond Sodium and Chlorine Nax r electron tir39anser from sodllum to chlorine a Kn b The sodium atom wants to lose its valance electron to become more stable c The chlorine atom wants to gain a valance electron to become more stable d The sodium atom gives its valance electron to the chlorine atom and both of them are happy ii Covalent bonds 1 2 Occur when atoms equally share their electrons with one another This occurs when the two interacting atoms are neither strongly electronegative or electropositive or have similar electronegativities Two or more atoms in a covalent bond constitute a molecule When covalent bonds form they release heat To beak a covalent bond the same amount of energy that was released as heat when the bond was formed is required This energy is called bond energy or BE The bonded atoms although attracted by their shared electrons are also repulsed by their like charges An equilibrium is created between the attraction and repulsion when the two atoms are at a specific distance from one another called the bond length Bond length and bond energy will vary amongst different atoms The more bonds there are double vs triple bond the shorter the bond length Example of a covalent bond a Carbon and Chlorine b Carbon is neither electropositive or electronegative c Carbon wants four more valance 1 u M electrons to become stable d Chlorine wants one more valance electron to become stable e Carbon will share each of it s four electrons with Chlorine to make a covalent bond 10 A single covalent bond can be drawn in many ways a A circle around the shared electrons b A line between the participating atoms 11 A double covalent bond can be drawn as two lines between the participating atoms 12 A triple covalent bond can be drawn as three lines between the participating atoms iii Polar Covalent Bond 1 A covalent bond in which the participating atoms do not equally share the electrons mvalerit Polar male rat bond mint 1 39 El Gl H GI Bonding pai r ILlll39lEEILIllhl39 Shared Example a covalent bond between a strongly electronegative atoms Bonding pair a equallyr shred and a weakly electronegative atom On the periodic table the more electropositive elements are on the bottom or towards the left On the periodic table the more electronegative elements are on the top or towards the right N a To determine which of the two participating atoms has the larger share of the electron look at their electronegativity s The element with the strongest electronegativity will have a larger share 5 When drawing a polar covalent bond use an arrow to indicate which H side has a stronger hold on the electron The arrow s head should be l pointed in this direction The arrow s tail will be oriented towards the In I r atom with a weaker hold on the electron with a bar drawn through it iv Multiple Covalent Bonds 1 Sometimes in order to become stable two atoms will share multiple 39OCQ3939 electrons 2 Example C02 a Carbon has four electrons and wants to gain four more electrons b Oxygen has six electrons and each oxygen atom wants to gain two more electrons 3 Each oxygen has four electrons that are not a part of a bond These electrons are called nonbonding or unshared electrons 4 When two electron pairs are shared a double bond is formed 5 When three electron pairs are shared a triple bond is formed c Carbon s Covalent bonds i The wide variety of organic compounds compounds with carbon comes from carbon s ability to covalently bond with multiple different elements and other carbon atoms ii An element s ability to form long chains of covalent bonds is called catenation Inert gas gas with a stable electron configuration a Considered stable because they do not need or quotwantquot to combine with other atoms Hydrocarbon molecules composed of hydrogen and carbon atoms alone a There are three hydrocarbons that will have two carbon atoms per molecule i Ethane Ethene and Ethyne b These three differ only in the number of hydrogens and whether they have a single double or triple covalent bond Valance a Valance is the potential number of bonds that an atom can form with other atoms b This is often the same number as the amount of electrons the atom needs to become stable The use of arrows a Arrows are used in structural formulas to represent many things b Curved arrow i This arrow is used to show hoe electrons are moved around to form different resonance structures ii The tail of the arrow shows where the electrons originated from iii The head triangle part of the arrow shows where the electrons will end up c Fishhookarrow i Similar to the curved arrow this arrow symbolizes the movement of a single electron ii The tail shows where an electron came from iii The head shows where the electron is going d Straight arrow 6 i A straight arrow shows is like an equal sign It points from the reactants to products in a chemical equation e Halfhead straight arrow i Like a normal straight arrow these point form the reactant to the product but also show that the equation is reversible f Double headed arrow H i These arrows are placed between two different structural formulas to indicate that they are resonance structures 10 The Shapes and Bonding of Orbitals a The different orbitals s p d and f have different shapes i s spherical ii p dumbbell shaped 1 Imagine a 3D xyz axis like the one you graph on 2 Each of the dumbbells is oriented on the x y or z axis n v p1 I I 3 b When atoms bond with one another they approach each other so that their orbitals ove ap i Atomic orbital the atom s orbit area ii Molecular orbital the orbital area taken up by bonded atoms 1 Both the atomic and molecular orbitals can hold up to two electrons iii Sigma 0 bonds 1 Sigma bonds can occur when two 5 orbitals overlap 2 Sigma bonds can occur when a s and p orbital overlap 3 Sigma bonds can occur when two p orbitals overlap 4 IMAGE FROM BOOK PAGE 23 AND 24 Figure 13 and 14 iv Pi 7 bond 1 When two properly aligned p orbitals bond a pi bond is formed 2 11 Electron Placement in Orbitals a The first orbitals to fill will be the ones in a lower number shell ls 2s ect b As shelf fill orbitals like p d and fwill be reached i When you reach the p orbital remember that there are there are three each able to hold two electrons for a total of six ii When you place electrons in the p orbitals you want to begin by placing one electron in each of the x y and z orbitals until each contains one electron Then if there are more you can place a second electron in each orbital as needed 1 If there three or less valance electrons they are placed in different x y or z orbitals because of electrons tendency to repulse one another c Remember that each orbital only holds two electrons 12 Hybrid Orbitals a Hybrid orbitals are handy ways of labeling what orbitals an atom is using b Hybrid orbitals are labeled with the participating orbitals and a superscript that tells how many parts are being used i sp3one part 5 and three parts p ii sp one part 5 and one part p c It is more likely to find electrons in the furthest lobe from the nucleus Each orbital is positioned as far as it can possibly get from the others MethaneCH4 has a regular tetrahedral shape It features carbon s sp3 and hydrogen s ls orbitals i The shape of an sp3 looks like the dumbbell shape of a p orbital with an exception the dumbbells are lopsided ii The bonds used in this shape are sigma bonds iii The bond angle created be each of the orbitals the sp3 is 1095 1 If you were to draw an imaginary line down the middle of each of the orbitals lengthwise this is the angle between these two lines An Sp 3 orbital 1095 Degrees Three dimensional representation of four sp3 hybrid orbitals centerd towards the corners of 2 a regular tetrahedron 0 Build this shape with your model kit 0 Note that two of the extending quotbondsquot are in the same plane as the carbon in the center of the shape 0 There should be one other bond pointing towards you and another pointing away from you 0 The planes of the protruding quotbondsquot are divided in half by the center and other two bonds that are in plane Text quotthe center and any two corners of a tetrahedron form a plane that is the perpendicular bisector of a similar plane formed by the center and the other two corners 13 Miscellaneous a b c d e The farther away from the nucleus the more energy an electron has Organic chemistry generally extends to the second row of the periodic table Degenerate energy no difference CH3 a methyl group Flipping a structure around does not create an isomer The two are identical Pictures Draw th httpchemistrvaboutcomodbervlliumaBervlliumsotopeshtm httpcnxorgcontentsa1fb5520d6b14d4c9cb059905b04ec12ZChemicalBondingIonic bonding httpwwwshodororgunchembasiclewis httpdronstudvcomquestionifweaddcarbonandchlorineitformsccl4but4isthe numberofelectronssowhvwesavoneatomofcarbonand4atomsofchlorinewhere4is numberofelectronsnotatoms httpwwwsuggestkevwordcomaGNslGvamQ httpchemistrvdeskblogspotcom201105polarandnonpolarcovalentbondhtml httpwwwmiddleschoolchemistrvcommultimediachapter4lesson6 httpwwwavogadrocoukorganicisomerhtm httpchempathschemeddlorgserviceschempathsqbookGeneral20Chemistrv20Textb ookChemicaIZOBonding2020Electron20Pairs20and200ctets1332polvatomicions httpchemistrvtutorvistacomorganicchemistrvcarbonbondinghtml httpwwwscienceoregonstateedu gablekCH334Chapter3chlorinationhtm httppubsrscorgencontentarticlelanding2014rpc4rp00057aunauthdivastract httponseectcompsspdorbitals15 httpwwwck12orguseramFinJfZBJhbnRpZXJAaGJv255vcmcsectionTheCovalentBond httpchemistrvtutorvistacomorganicchemistrvhvbridorbitalshtml httpwwwedinformaticscominteractive molecules3Dmethane moleculehtm httpwebpdxeduquot39wamsercC334F981noteshtm httpscommonswikimediaorgwikiFileMethane3Dspacefillingpng Lecture slides e shells and orbitals For resonance structures will the formal charge be whole or partial Are the funky arrows for isomers Page 21 Bottom of paragraph 2
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