CH104Exam2StudySoup.pdf CH 104
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This 10 page Study Guide was uploaded by Regan Dougherty on Thursday October 1, 2015. The Study Guide belongs to CH 104 at University of Alabama - Tuscaloosa taught by Stephen Woski in Summer 2015. Since its upload, it has received 151 views. For similar materials see Introductory Chemistry in Chemistry at University of Alabama - Tuscaloosa.
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Date Created: 10/01/15
Exam Date 10615 Chemistry 104 Exam 2 Chapters 3 amp 4 Woski s favorite Hockey Team Detroit Red Wings Chapter 3 Ionic Compounds Introduction to Bonding BONDING the joining of two atoms in a stable arrangement Noble gases do not readily react to form bonds In bonding elements gain lose or share electrons to attain the electronic configuration of the noble gas closest to them in the periodic table IONIC BONDS result from the transfer of electrons from one element to another form between a metal left side of the periodic table and a nonmetal right side composed of ions charged species in which the number of protons and electrons in an atom is not equal ions with charges are attracted to each other COVALENT BONDS result from the sharing of electrons between two atoms formed when two nonmetals combine or when a metalloid bonds to a nonmetal MOLECULE compound or element containing two or more atoms joined together with covalent bonds Ions Ionic compounds consist of oppositely charged ions that have a strong electrostatic attraction electrical attraction between oppositely charged ions for each other CATIONS positively charged ions fewer electrons than protons have lost electrons metals form cations Exam Date 10615 ANIONS negatively charged ion more electrons than protons have gained electrons nonmetals form anions goal of ionic compounds completely filled shell of electrons OCTET RULE a main group element is especially stable when it possesses an octet of electrons 8 electrons in its outer shell atoms like to have a noble gas configuration which is usually 8 electrons but there are exceptions Relating Group Number to lonic Charge for Main Group Elements Elements in the same group from ions of similar charge For metals in groups 1A 2A and 3A the group number the charge on the ca on For nonmetals in groups 5A 6A and 7A the anion charge 8 the group number Group 1A 1 lose1 electron charge 1 2A 2 lose 2 electrons charge 2 3A 3 lose 3 electrons charge 3 5A 15 gain 3 electrons charge 3 6A 16 Exam Date 10615 gain 2 electrons charge 2 7A 17 gain 1 electron charge 1 Transition Metals more than one charge is possible the charge is normally indicated by roman numerals after the name ex Chromiumll no space Another way to indicate charge ion with the lower charge end in ous and the ion with the high charge end in ic know copperl is cuprous copperll is cupric ironll is ferrous ironlll is ferric tinll is stannous tinlV is stannic lonic Compounds When a metal transfers one or more electrons to a nonmetal ionic bonds are formed lonic compounds are composed of cations and anions The sum of the charges in an ionic compound must always be zero overall Naming lonic Compounds CHEMICAL NOMENCLATURE assigning an unambiguous name to each compound It is typical to add ion after the name of the metal cation If a metal is able to form two different cations follow the name of the cation by a Roman numeral in parentheses to indicate its charge OR use the suffix ous for the cation with the lesser charge and the suffix ic for the cation with the higher charge Exam Date 10615 the suffixes are usually added to the Latin names of the elements know copperl is cuprous copperll is cupric ironll is ferrous ironlll is ferric tinll is stannous tinlV is stannic Anions are named by replacing the ending of the element name by the suffix ide To name an ionic compound with a main group metal cation whose charge never varies name the cation and then the anion do not specify the charge or how many ions of each type are needed to balance charge If the ionic compound contains a metal with variable charge specify the charge of the cation in the name a compound has no charge neutral you may need a ratio other than 11 for some element combinations this needs to be considered when writing formulas Physical Properties of lonic Compounds crystalline solids held by extremely strong interactions of the oppositely charged ions very high melting points very high melting points many are soluble in water When an ionic compound dissolves in water the ions are separated and each anion and cation is surrounded by water molecules Polyatomic lons POLYATOMIC ION cation or anion that contains more than one atom atoms are held together by covalent bonds The names of polyatomic ions end in the suffix ate hydroxide and cyanide are exceptions The suffix ite is used for an anion that has one fewer oxygen atom than a similar anion named with the ate ending Exam Date 10615 When two anions differ in the presence of a hydrogen the word hydrogen or the prefix bi is added to the name of the anion Chapter 4 Covalent Compounds Introduction to Covalent Bonding COVALENT BOND a twoelectron bond in which the bonding atoms share valence electrons MOLECULE discrete group of atoms held together by covalent bonds We use a solid line between two element symbols to represent a twoelectron bond Diatomic Molecules contain just two atoms H2 02 N2 F2 CI2 BI 2 I2 Unshared electron pairs are called non bonded or lone pairs In covalent bonding atoms share electrons to attain the electron configuration of the noble gas closest to them in the periodic table Covalent bonds are formed when two nonmetals combine or when a metalloid bonds to a nonmetal LEWIS STRUCTURE an electrondot structure for a molecule that shows the location of all valence electrons in the molecule both the shared electrons in bonds and the non bonded electron pairs Atoms with one two or three valence electrons generally form one two or three bonds respectively Atoms with four or more valence electrons form enough bonds to give an octet predicted bonds 8 number of valence electrons Lewis Structures MOLECULAR FORMULA formula that shows the number and identity of all the atoms in a compound but does not indicate what atoms are bonded to each other A Lewis structure shows the connectivity between the atoms as well as where all the bonding and nonbonding valence electrons reside Exam Date 10615 Rules for Lewis Structures Draw only the valence electrons Give every main group element except hydrogen and octet of electrons Give each Hydrogen two electrons Lines represent bonds Drawing Lewis Structures arrange atoms with those bonded next to each other H and halogens on the periphery because they only form one bond count valence electrons place one bond between neighboring atoms give every atom an octet of electrons using lone pairs exception H can only have 2 electrons use multiple bonds when one atom does not have an octet Exceptions to the Octet Rule Hydrogen is an exception because it accommodates only two electrons in bonding gives is a He configuration Li also has a He configuration and Be2 not an octet but it is a noble gas configuration Elements in group 3A do not have enough valence electrons to form an octet in a neutral molecule Some elements in the third row of the periodic table have empty d orbitals available to accept electrons so they may have more than 8 electrons around them Boron is happy with 3 valence electrons H has zero electrons just a proton Exam Date 10615 Resonance We sometimes must draw Lewis structures for ions that contain covalent bonds polyatomic ions Add one electron for each negative charge subtract one electron fro each positive charge RESONANCE STRUCTURES two Lewis structures having the same arrangement of atoms but a different arrangement of electrons Two resonance structures differ in the location of multiple bonds and the position of lone pairs The actual structure is a hybrid of the two resonance structures A doubleheaded arrow is usually used to show that two Lewis structures are are resonance structures drawn between the two structures HYBRID a composite of two or more resonance forms Resonance stabilizes a molecule by spreading out lone pairs and electron pairs in multiple bonds over a larger region of space A molecule of ion that at has two or more resonance structures is resonance stabilized Naming Covalent Compounds Step 1 name the first nonmetal by its element name and the second using the suffix ide Step 2 add prefixes to show the number of atoms of each element mono di tri tetra penta hexa hepta oct nona deca Mono is omitted when only one atom of the first element is present but it is retained for the second element The less electronegative element is usually first Molecular Shape How many groups surround the atoms A group is either an atom or a lone pair of electrons Exam Date 10615 VALENCE SHELL ELECTRON PAIR REPULSION VSEPR THEORY a theory that predicts molecular geometry based on the fact that electron pairs repel each other thus the most stable arrangement keeps these groups as far away from each other as possible Ignore multiple bonds in predicting geometry Count only atoms and lone pairs Linear An atom surrounded by two groups is linear and has a bond angle of 180 The outside molecules want to be as far apart as possible 39 ex CO2 and HCN Trigonal Planar An atom surrounded by three groups is trigonal planar and has bond angles of 120 39 ex BF3 Tetrahedral An atom surrounded by four groups is tetrahedral and has bond angles of 1095 39 ex CH4 has a 3D geometry A solid line is used for bonds in the plane A wedge is used for a bond in front of the plane A dashed line is used for a bond behind the plane A group can also be a lone pair of electrons Lone pairs of electrons take up space just like bonds do Trigonal pyramidal tetrahedral with a lone pair instead of a molecule on the top of the molecule 3 atoms and one lone pair 39 ex NH3 Exam Date 10615 BentShape 2 atoms with 2 lone pairs Electronegativity and Bond Polarity Not all atoms in covalent bonds share electrons equally In this case electrons are more closely associated with one atom than the other ELECTRONEGATIVITY is a measure of an atom s attraction for electrons in a bond how mach a particular atom wants electrons value from O to 4 the higher the value the more electronegative an atom is and the more it is attracted to the electrons in a bond Electronegativity increases across a row of the periodic table as the nuclear charge increases excluding the noble gases Electronegativity decreases down a column of the periodic table as the atomic radius increases pushing the valence electrons farther from the nucleus Nonmetals are more electronegative than metals The most electronegative elements FI and O are located in the upper right corner of the periodic table NONPOLAR BOND a bond where electrons are equally shared when atoms with similar electronegativities are bonded together occurs between atoms of the same element C H bonds are nonpolar Polarpolarcovalent bonds result form bonding between atoms with different electronegativities DIPOLE partial separation of charge in a bond or molecule A polar bond will usually be one in which the electronegativity difference between two atoms is 05 units or greater electrons are unequally shared pulled toward the more electronegative element Exam Date 10615 Ionic Bond electrons are transferred rom the less electronegative element to the more electronegative element greater than 19 unit difference metal and nonmetal electronegativivties for metals are lower than nonmetals Polarity of Molecules A molecule with no polar bonds is a nonpolar molecule A molecule with one polar bond is a polar molecule If the individual bond dipoles do not cancel the molecule is polar If the individual bond dipoles cancel the molecule is nonpolar Check out Quizlet for polyatomic ion flash cards we have to memorize those My username is rmdoughertyf use of the flash cards is completely free Let me know if you have any questions Good luck and happy studying 1O
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