CHM103 Exam 2 Study Guide
CHM103 Exam 2 Study Guide 103
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This 17 page Study Guide was uploaded by askcch on Sunday October 16, 2016. The Study Guide belongs to 103 at University of Miami taught by Elliot Atlas in Fall 2016. Since its upload, it has received 30 views. For similar materials see Chemistry for Life Sciences I (Lecture) in Chemistry at University of Miami.
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Date Created: 10/16/16
CHM103 Class otes eek (9/199/23) ________________________________________________________________________________ From revious ections 2.42.8 Periodic Table, Characteristics of Different Groups, Electron Configuration ________________________________________________________________________________ Chapter 3: Ionic Compounds 3.1 ons Alkali metals (group 1A) form compounds with halogens (group 7A) Properties of these compounds include: High melting points Stable, hite, crystalline solids Soluble in water Conduct lectricity hen issolved in water * Electricity can only flow through a medium containing charged particles (ions) hat are ree to ove An ion is formed when a neutral atom gains or loses electrons The loss of electron(s) gives a positively charged ion called a cation The gain of electron(s) gives a negatively charged ion called an anion Positive charge = ;Negative charge = (which n is any integer) 3.2 Ions and he ctet Rule Octet rule: Main group elements tend to undergo reactions that leave them with eight valence lectrons E.g. Alkali metals with a single valence electron react with halogens with seven valence electrons, giving both ns np 6 configurations with eight valence electrons (i.e. noble gas electron configuration) 2 2 3 3 2 2 6 E.g. N: 1s 2s 2p → N : 1s 2s 2p 3.3 ons of Some ommon Elements Transition metals form cations, but they can lose one or more d electrons in addition to losing alence electrons. he octet ule is not ollowed. Metals form cations by losing one or more electrons Reactive nonmetals form anions by gaining one or more electrons to achieve a noble as configuration Group 8A elements (noble gases) are nreactive Ionic charges of main group elements can be predicted using the group number and the octet ule E.g. 1A = ,2A X E.g. A X , 6A = , A X CHM103 Class otes eek (9/269/30) __________________________________________________________________________ ______ From revious ections 3.13.3 Ions, octet rule, etc. __________________________________________________________________________ ______ Chapter 3: Ionic Compounds 3.4 eriodic roperties and Ion Formation Ionization nergy is the nergy required to remove one electron from ingle atom in the aseous state Small values indicate ease of losing electrons to form cations Electron ffinit is he energy eleased on adding n electron to single atom in the aseous state Halogens have the largest values and gain electrons most easily ● Halogens ain lectrons ost easily ● Alkali metals lose electrons most easily ● Noble gases neither lose nor gain electrons ● Elements near the middle of the periodic table do not form ions easily 3.5 Naming Monatomic Ions Main group metal cations are named by identifying the metal, followed by the word ion Transition metals can form more than one type of cation Anions are named by replacing the ending of the element name with ide, followed by the ord ion 3.6 olyatomic ons The atoms in a polyatomic ion are eld together by ovalent bonds Itis charged because it contains a total number of electrons that is different from the total number of protons in the combined atoms 3.7 Ionic Bonds Iontransfer reactions of metals and nonmetals form products unlike either element Positive cations bond with negative anions to form ionic bonds 3.8 Formulas of Ionic Compounds All chemical (Ionic) ompounds are eutral Once the ions are identified, decide how many ions of each type give a total charge of zero The chemical formula of an ionic compound tells the ratio of anions and cations When the two ions have different charges, the number of one ion is equal to the charge n he other ion The formula of an ionic compound shows the lowest possible ratio of atoms and is known as a simplest formula Formula unit: The formula that identifies the smallest neutral unit of an ionic compound + For NaCl, the formula unit is one Na ion and one Cl ion For CaF , 2 the formula unit is one Ca ion and two F ions Formula = (cation)(anion) Do not write the charges of the ons Use parentheses around a polyatomic ion formula if i has a subscript Al2 SO )4 3 CHM103 Class otes Week 7 10/0310/07) ________________________________________________________________________________ From revious ections 3.43.8 Ion formation, Ionic formulas, etc. ________________________________________________________________________________ Chapter 3: Ionic Compounds 3.9 Naming Ionic Compounds There are two inds of ionic compounds: Type onic ompounds contain cations main group elements The charges on these cations do not ary Do not pecify he harge on the cation NaCl is sodium chloride, MgCO ismagnesium carbonate 3 Type I onic compounds contain metals that an exhibit more than ne charge Specify the charge on the cation in these compounds with either the old (ous, ic) or the new (roman numerals) system FeCl 2 is iron (II) chloride or ferrous chloride FeCl 3 is iron (III)chloride or ferric chloride 3.10 Some Properties of Ionic Compounds Ions in an ionic solid are held rigidly in place by attraction to their neighbors Once an ionic solid is dissolved in water, the ions can move freely, which accounts for the electrical conductivity of these compounds in solution Ionic compounds have very high melting and boiling points Ionic compounds dissolve in water i the attraction between water and the ions overcomes the attraction of the ions for one another. Not al ionic compounds are water soluble 3.11 H and OH ions: An Introduction to Acids and Bases Acid: A substance hat provides H ions n water A hydrogen cation is imply roton When an acid dissolves in water, the proton attaches to a molecule of water + to form a ydronium ion (H 3 ) + Different acids can provide different numbers of H ions per acid molecule Base: A ubstance that provides H ions n water A hydroxide anion is a polyatomic ion, OH through covalent bond When these compound dissolve, OH anions go into solution along with the metal ation Different bases can provide different numbers of OH ions per formula unit Naming Ionic Compounds Naming Acids CHM103 Class N otes Week 8 10/1010/14) ________________________________________________________________________________ From revious ections 3.93.11 Naming ionic ompounds, acids, etc. ________________________________________________________________________________ Chapter : olecular Compounds 4.1 ovalent Bonds Covalent ond: bond formed by haring lectrons between atoms Molecule: group of atoms held ogether by covalent bonds Some naturally ccuring diatomic molecules 4.2 ovalent onds and he Periodic able A molecular compound is a compound that consists of molecules rather than ions Exceptions to the ctet rule: Boron has only three electrons to share, and forms compounds in which i has only three ovalent onds and i electrons Elements in the third row down have vacant orbitals, allowing them to have an expanded octet 4.3 Multiple ovalent Bonds The bonding in some molecules cannot be explained by the sharing of only two electrons etween toms Therefore, a double or triple bond isformed (e.g. CO and N ) 2 2 Carbon, nitrogen, and oxygen are the elements most often present in multiple bonds Carbon and nitrogen can form double or triple bonds Oxygen forms nlydouble bonds Note that ub compounds containing multiple bonds, carbon stil forms four covalent bonds, nitrogen stillforms three, and oxygen stil forms two covalent bonds 4.4 Coordinate Covalent Bonds The covalent bond that forms when both electrons are donated by the same atom Once formed, a coordinate covalent bond is no different from any other covalent bond 4.5 haracteristics of Molecular Compounds Ionic compounds have high melting and boiling points because the attractive forces between oppositely harged ions are so strong Molecules are neutral, so there isno strong electrostatic attraction between molecules 4.6 Molecular ormulas and ewis Structures A molecular formula gives the numbers and kinds of atoms that are combined in one molecule An ionic formula ives only ratio ions Structural ormula: olecular epresentation that shows the onnections among atoms by using lines to represent covalent bonds Lewis structure: A olecular representation that hows both the connections among atoms and the locations of lonepair valence electrons 4.7 Drawing Lewis Structures 1. Find the total number valence electrons of all atoms in the olecule r i on or an ion, add one electron or each egative charge or ubtract one for each ositive harge. 2. Draw a line between each pair of connected atoms to represent the two electrons in a covalent bond. 3. Using the remaining electrons, add lone pairs so that each atom connected to the central tom except H) gets n octet. 4. Place any remaining electrons in lone pairs on the central atom 5. If the central atom does not have an octet after allelectrons have been assigned, take a lone pair from a neighboring atom and form a multiple bond to the central atom Common bonding patterns for C, N, O, X (Halogen), and H 4.8 The Shapes of Molecules ValenceShell ElectronPair Repulsion (VSEPR) odel VSEPR isa method for predicting molecular shape by noting how many electron charge clouds surround atoms and assuming that the clouds orient as far away from one another as possible 1. Draw a Lewis structure of the molecule, and identify the atom whose geometry is of interest usually he central atom) 2. Count the number of electron charge clouds surrounding the atom of interest (total number of lone pairs plus bonds to other atoms of the central atom, count multibond only once) 3. Predict molecular shape by assuming that the charge clouds orient in space so that they are as far away from one another as possible A bond angle is the angle formed by three adjacent atoms in a molecule o Linear molecules result with bond angles of 180 . Trigonal planar molecules result with bond angles of 120 . Ifone of the charge clouds is a lone pair, the molecule will be bent. o Tetrahedral molecules result with bond angles of 109.5 . Lone pairs repel strongly, reducing bond angles slightly The geometry around atoms in larger molecules also derives from these same shapes 4.9 Polar ovalent Bonds and Electronegativity A olar covalent bond i one i hich the electrons are ttracted more strongly by one atom than by he other Electronegativity: he ability of an tom to attract electrons in a covalent ond Electronegativity generally decreases going from right to left in the periodic table Metallic lements have ow electronegativities Halogens nd eactive onmetal elements have igher lectronegativities Electronegativity generally decreases going down the periodic table within a group 4.10 olar Molecules Entire molecules can e olar if electrons are attracted ore strongly to ne part fthe molecule Molecular polarity is due to individual bond polarities and lonepair contributions. Electrons are displaced toward the more electronegative atom Symmetrical molecules can have polar bonds and be nonpolar overall 4.11 Naming Binary Molecular Compounds Binary Compound: A compound formed by a combination of two different elements When writing molecular formulas of binary compounds: The lesser electronegative element is written first Metals are always ritten before nonmetals A nonmetal farther lef on the periodic table generally comes before a nonmetal farther right Step 1: Name the first element in the formula, using a prefix i needed to indicate the number of atoms Step 2: Name the second element in the formula and modify by adding the ide suffix as when naming anions. Include numerical prefixes as appropriate
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