Exam 3 Study Guide - Finnegan
Exam 3 Study Guide - Finnegan Chemistry 105
Popular in Chem 105: Principles of Chemistry
Popular in Chemistry
This 11 page Study Guide was uploaded by Emma Silverman on Sunday April 12, 2015. The Study Guide belongs to Chemistry 105 at Washington State University taught by Finnegan in Spring2015. Since its upload, it has received 502 views. For similar materials see Chem 105: Principles of Chemistry in Chemistry at Washington State University.
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Date Created: 04/12/15
CHEM 105 Topics for the third exam Spring 2015 0 Electron configurations ground state electron configurations of monatomic ions 1Use the noble gas notation to show the ground state electron configuration of As Ar 4323d 04p3 Sb Kr 5sz4d 05p3 Bi Xe 6324f 45d 06p3 main group ions transition metal ions orbital diagrams paramagnetic vs diamagnetic If an atom or ion has unpaired electrons it is paramagnetic If all the electrons are paired the atom or ion is diamagnetic 1How many unpaired electrons are present in the ground state of cobalt 3 the first and second box of the d orbital will be paired and the other 3 won t be 2Cassify the ground state of sulfur as paramagnetic or diamagnetic Paramagnetic 3Cassify the ground state of zinc as paramagnetic or diamagnetic Diamagnetic 0 Periodic trends definitions trend direction explanation based on electron configurations irregularities due to full and halffull subshells Halffilled sublevels are more stable lower energy than any other partially filled configuration This explains some anomalies in the ground state electron configurations CrAr4s 3d5 rather than Ar4323d4 CuAr4s 3d1O rather than Ar4323d9 You should be aware that such anomalies exist You DO NOT need to memorize them No exam questions on them atomic radii Atomic radii atoms tend to be larger as you move left and down on the periodic table 1Arrange the following elements in order of increasing atomic size atomic radius CI lt P lt Ge lt Sn the closer to the bottom left they are the bigger their radius ionic radii 1Which of these has the larger radius A Mg B Mg2 2Which of these has the larger radius A F B F39 Anions are larger than the parent atom Cations are smaller than the parent atom The larger the charge the greater the change in size ionization energy Ionization energy IE The 1st ionization energy gets larger more positive as you move right or up on the periodic table This is the opposite of the trend in atomic radii THe smaller the atom the closer the electron is the the nucleus and the harder it is to remove Note the anomalies due to the stability of filled and halffilled subshells Each subsequent electron takes more energy to remove IE2ltIE1 why 1Which atom has a higher IE1 Sn Ge 2Which atom has a higher IE1 AN 80 3The following are successive ionization energies for an atom Which one indicates the first removal of a core electron IE1 736 kJmol IE2 1445 kJmol IE3 7730 kJmol IE4 10600 kJmol IE5 13600 kJmol IE1 IE2 IE3 IE4 IE5 W999 4At what ionization energy if titanium does the energy quotjumpquot significantly IE1 IE2 IE3 IE4 IE5 IE6 IE7 IE8 Has four valence electrons so it s the one after that 5 electron affinity 6Which chemical equation corresponds to the first electron affinity of bromine AH EA1 A Br2 l 2 e39 gt 2 Br g B Br2 g 2 e39 gt 2 Br39 g C Br2 l e39 gt Br39 g Br g Iomrnuowgt Brz g e gt Br 9 Br 9 Br I e39 gt Br39 g Br 9 e39 gt Br 9 12 Br2 g e39 gt Br g QT39FF39U Electron Affinity EA Atoms in the gas phase The first electron affinity for an atom tends to decrease AH becomes more negative as you move right or up on the periodic table Smaller atoms release more energy when you add an electron because the electron gets closer to the nucleus Note the severe exceptions due to the stability of filled and halffilled shells The second and subsequent electron affinities are always positive Why 1Which atom the more negative EA1 A S B Cl Always the halogen 0 Lewis electron dot symbols for atoms and monatomic ions Draw Lewis dot symbols for the following 0 6 valence two sides with two dots and two sides with one dot Ca 2 valence one dot on two sides Ge 4 valence one on each side Ar 8 valence electrons two on each side 8239 8 valence electrons two on each side plus a 239 l398 valence electrons two on each side plus a 39 Octet Rule Main group elements gain lose or share electrons to achieve a set of eight valence electrons Dot symbols for ionic compounds Potassium iodide K8 valence electrons Iodine with 8 electrons plus a 39 Sodium oxide twice as many sodium as oxide oxygen with 8 dots and a 239 plus Na Some guidelines for Lewis structures Use the central atom premiss One atom in the center with the other connected to it Molecules with multiple C or N will tend to have multiple centers C is the only element that forms long chains of itself Avoid 00 and FF bonds Never make chains of O or F Don t make triangles or squares F does not form double bonds ever C N O and F must obey the octet rule no exceptions for these elements The formal rules for drawing Lewis structures are in section 97 p398399 1 skeletal structure central atom is least electronegative Except hydrogen 2 valence electron count 3 octets 4 multiple bonds as necessary 0 Ionic bonds Ionic Bonds the electrostatic attraction between two ions of opposite charge Electron transfer is required to form ions but is not part of the bond When NaCls forms it does not form one ionic bond lattice energy The ions form into a lattice a three dimensional array of ions Each ion forms many ionic bonds The formation of these bonds releases energy This is called the lattice energy lonic bonds are delocalized Coulomb s Law see page 389 1Which of the following ionic compounds has the most negative lattice energy A NaCl B RbCl Na is smaller than Rb so it is more negative Bigger charges are also more negative 2Which of the following ionic compounds has the most negative lattice energy A MgO B NaF 2x2 vs 1x1 If the charges differ and the sizes disagree go with the charges 3Which of the following ionic compounds has the most negative lattice energy A Ca3P2 B Ca3N2 The charges are the same so look at size N is smaller than P 4Which of the following ionic compounds has the most negative lattice energy A KBr B KZS Larger charges means more negative lattice energy BornHaber cycles A BornHaber cycle see 387 Consider the energies involved in forming sodium oxide 0 Covalent bonds A covalent bond requires a balance of forces attractive forces electronnucleus electronelectron The distance between two atom linked by a covalent bond is the distance at which the attractive and repulsive forces balance each other This is a position of minimum energy energy is released when a bond is formed Covalent bonds are localized They exist between a specific pair of atoms Know the relationship between bond length bond strength bond energy and bond order bond energystrength 1Arrange the following in order of increasing bond strength bond energy PCLltPOltSO 2Rank the following NN bonds in increasing bond energy NNltNNltNEN bond length 1Arrange the following in order of increasing bond length 80 lt PO lt PCl 2Rank the following 00 bonds in increasing bond length CEC lt CC lt CC polar covalent bonds Polar covalent bonds bonds in which the electrons are shared unequally between two atoms Electronegativity is a measure of an atom s ability to attract electrons in a covalent bond The electrons will spend more time near the atom with the highest electronegativity 1Rank the following bonds in order of increasing polarity HSi lt ClO lt PBr lt HN lt SO lt CF lonic character Polar bonds can be thought of as a combination of a covalent and an ionic bond THe more polar the bond the higher the percentage of ionic bonding to covalent bonding 2Rank these bonds in order of increasing percent ionic character AsBrltASltHOltKClltLiF electronegativity Generally increases across a period in the periodic table Generally decreases down a column in the periodic table Fluorine is the most electronegative Francium is the least electronegative 0 Lewis structures 1Write the skeletal structure 2Calculate the number of valence electrons 3Distribute the electrons assuring there is octets 4lf any atoms lack an octet form a double or triple bond resonance structures How many resonance structures must be drawn for each of the following draw them nitrous acid HNO2 1e395e392x6e3918e39 ONOH 42 2 O Nitrite ion N0239 5e392x6e391e3918e39 ONO 624 ONO 426 Nitric acid 1e395e392x6e3924e39 When molecules have multiple Lewis structures they are called resonance structures bond order Bond order of electrons in bonding molecular orbital of electrons in antibonding molecular orbital 2 A positive bond means there are more electrons in the bonding molecular orbitals than the antibonding A negative or zero bond order means there won t be a bond formed formal charge The formal rules for drawing Lewis structures are in section 97 p398 399 skeletal structure central atom is least electronegative Except hydrogen valence electron count octets multiple bonds as necessary 99 F Draw Lewis structures for H202 HOOH 4 dots on the O s 1Which of the following is the best Lewis structure for formaldehyde l i o H c f Structure 1 i i Structure 2 Structure 3 Structure 4 0 Structure 1 0 Structure 2 0 Structure 3 0 Structure 4 Answer D 2What is the formal charge on the left chlorine in the following structure 13 Cl Cl Answer 0 3What is the formal charge on the oxygen in the following structure 6 CI Cl Answer 1 4What is the formal charge on the carbon in the following structure III ci cl Answer 0 5What is the formal charge on the right chlorine in the following structure III U m GI Answer 1 6What is the formal charge on the left chlorine in the following structure 1 Eil 39ru Ell Answer 0 7What is the formal charge on the oxygen in the following structure 1 i l g El I Answer 0 8What is the formal charge on the carbon in the following structure i a Eil Answer 9What is the formal charge on the right chlorine in the following structure 1 Answer 0 o Valence Shell Electron Pair Repulsion Theory VSEPR Groups of valence electrons around an atom will tend to get as far apart from each other as possible geometry electron pair geometry The electron geometry determines the ideal bond angles approximate bond angles Electron geometry and the number of lone pairs determines the Molecular Geometry Molecular Shape The number of electron groups determines the Electron Geometry Linear geometry two electron groups Trigonal planar geometry three electron groups Tetrahedral geometry four electron groups Trigonal bipyramidal geometry five electron groups octahedral geometry six electron groups What is the electron geometry around the central atom in l339 0 near trigonal planar bent tetrahedral trigonal pyramid trigonal bipyramidal seesaw Tshaped octahedral square pyramidal square planar molecular shape molecular geometry The Molecular Shape the bond polarities and the formal charge distribution determine the Molecular Polarity see table 101 on page 434 NOT GOING TO BE ON EXAM KNOW THEM AXE class The AXE type of a compound can be found from a valid Lewis structure AXnEm n of bonding groups on the central atom m of lone pairs on the central atom Any type of bond single double or triple is one bonding group nm the number of electron groups on the central atom bond angles The electron geometry determines the ideal bond angles approximate bond angles Lone pairs take up more space than bonding pairs see section 103 Double bonds take up more space than single bond see page 427 orbital hybridization polarnonpolar molecules 0 Valence bond theory hybrid orbitals Hybrid orbitals are named from the orbitals that contribute to them sp2 are a combination of one s and two p orbitals Note all of the orbitals that are mixed must come from the same shell same value of n The total number of orbitals is unchanged there will be two sp orbitals three sp2 orbitals four sp3 orbitals etc Each type of hybrid orbital is associated with a specific electron geometry 1What is the orbital hybridization on the central atom in SeOZ SP sp3 sp3d sp3d2 2What is the orbital hybridization on the central atom in PCI3 SID SID SP sp3d sp3d2 2 3 3What is the orbital hybridization on the central atom in SO42 SP sp3 sp3d sp3d2 obonds and Trbonds delocation of Trbonds Single bonds are formed by the overlap of orbitals in the region between the atoms Such bonds are called sigma 0 bonds Double and triple bonds also contain a 0 bond but the second and third bond cannot form directly between the atoms there is already a pair of electrons there The additional bonds are formed by unhybridized porbitals that overlap in the areas to either side of the 0 bond Such bonds are called pi 1T bonds How many sigma bonds and how many pi bonds are present in the following molecule EH c BEN quota I C H 21 5 some are unseen in the CH3s o Titrations Review Labs Acid base Experiments 4 amp 5 Review Labs Redox titrations Experiment 10 Review Labs equivalence point vs end point Review Labs indicators Review Labs
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