Popular in Chemistry Chapter 8 and 9
Popular in Chemistry
This 6 page Class Notes was uploaded by Ali Bedbury on Monday February 9, 2015. The Class Notes belongs to CHEM 221 at University of Oregon taught by watt in Fall. Since its upload, it has received 43 views. For similar materials see Chemistry Chapter 8 and 9 in Chemistry at University of Oregon.
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Date Created: 02/09/15
83 Trends in the Three Atomic Properties AtOmiC size how closely one atom lies next to another Varies slightly from substance to substance 1 Metallic radius used for metals one half the shortest distance between nuclei of adjacent atoms in a crystal 2 Covalent radius used to molecules mostly non metals ne hald the shortest distance btwn nuclei of bonded atoms MainGroup Elements atomic size varies within groups and periods as a result of two opposing in uences the net effect of these in uences depends on how effectively the inner electrons shield the nuclear charge 1 Changes in n principal quantum number as this increases probability that the outer electrons spend most of their time farther from the nucleus increases THUS ATOMIC SIZE INCREASES 2 Changes in Zeff effective nuclear charge increases outer electrons are puled closer to the nucleus this atomic size decreases Down a group n dominates each level has one more level of inner electrons Even though additional protons do moderatelt increase Zeff for the outer electrons the atoms get larger as a result of increasing n value Atomic radius generally down a group Across a period Zeff dominates Across a period from left to right electrons are added to the same outer level so the shielding by inner electrons does not change Despite great electron reuplsions outer electrons shield each other only slightly Zeff rises signicantly and outer electrons are pulled closer to nucleus Atomic radius generally down a period Transition Elements shows size trends are not consistent 1 Down a transition group n increases 2 Across a transition series atomic size shrinks for the rst 2 or 3 elements and then is constant 3 The size decrease across Period 4 is greater than Periods 5 and 6 l0 lzatIOn Energy energy required fort removal of 1 mol of electrons from 1 mol of gaseo ps 1t Always positive Endothermic Atoms with a low IE tend to form cations Atoms with a high IE tend to form anionsrasq w o The second IE is always higher than the This increase includes an enormous jum electrons have been removed beacause Energy is needed to removed an inner core electron Periodicity of First Ionization Energy as size decrease it takes more energy to remove an electron because the nucleus is closer so IE 1 increases 1 Down a group n value increases so atomic size increaeas but the distance from nucleus to outer electrons increase so attraction lessns and it is easier to remove IE generally decreases down a group 2 Across a period As you move left to right across a period Zeff generally increase and atomic size decreases and the attration increases so the electron is harder to remove lE generally increases across a period Electron is the energy required to change kjmol accompanying the addition of 1 mol of electrons to 1 mol of gaseous atoms or ions The rst electron af nity refers to the formation of 1 mol of monovalent gaseous anions Not as patterned exceptions arise from changes in sublevel energy and electronelectron repulsion Overall trend in electron af nities is to increase from left to right across a period 0 Measure of how readily an element forms an anion Noble gases high IE and low EA Nonmetals high IE and high EA Metals low IE and low EA 84 Atomic Properties and Chemical Reactivity Trends in Metallic Behavior 0 Metallic behavior decreases left to right across a period and increase down a group 0 Exceptions graphite nonmetallic carbon is a good conductor nonmetal iodine is shiny Metallic gallium melts mercury is a liquid iron is brittle Down a main group increase in metallic behavior and decrease in IE Across a period decrease in metallic behavior and decrease in size and increase in IE Redox behavior of the MainGroup Elements related to an elements tendacny to lose or gain electrons is its redox behavior whether it behaves as an OXIDIZING AGENT or REDUCING AGENT and the associated changes in its oxidation number You can dins the highest and lowest oxidation numbers of many main group elements from the periodic table 0 The A group is usually the highest ON always positive of any element in the group excpetions are O and F 0 Nonmentals and metalloids A group number minus 8 is the lowest ON always negative Members of the IA1 and 2A2 lose electrons readily so they are strong reducing agents AcidBase Behavior of Oxides metals are also distinguished from nonmetals by the acidbase behavior of their oxides in water 0 Most maingroup metals transfer electrons to oxygen so their oxides are ionic In water these oxides act as bases producing OH ions from 02 and reacting with acids Nonmetlas share electrons with oxygen so nonmetal oxides are covalent They react with water to from acids producing H ions and reacting with bases 0 So many metals and metalloids form oxides that are amphoteric they can act as acids or bases in water Properties of Monatomic Ions 1 Ions with a noble gas con guration have very low reactivity because their highest energy level is full This when elements either end of a period from ions they attain a lled outer level a noble gas con guration These ions are ISOELECTRONIC with the nearest noble gas 2 Ions without a noble gas con guration metals of 3A13 to 5A 15 a Pseudonoble gas con guration if the metal atom empties its highest energy level it attains the stability of empty ns and np sublevels and lled inner sublevels Electron Con gurations of Transition Metal Ions metal ions rarely attain a noble gas con guration expect scandium and titatnium Outer electrons are removed rst 0 Main group sblock metals lose all electrons with the highest n value 0 Maingroup pblock metals lose np electrons before ns electrons 0 Transition 9dblock0 metals lose ns electrons before n1d electrons o Nonmetals gain electrons in the p orbitals of highest n value Magnetic Properties of Transition Metal Ions electron spin generates a tiny magnetic eld causes a beam of H atoms to split in an external magnetic eld species with unpaired electrons that is attracted by an external eld it isnotattracted and is slightly repelled by the eld Man Ionic Size vs Atomic Size the ionic radius is a measure of the size of an ion and is obtained from the distance between the nuclei of adjacent ions in a crystalline ionic compound From the relation between Zeff and atomic size we can predict the size of an ion relative to its parent atom Cations are smaller than parent atoms because electrons are removed Anions are larger than parent atoms Down a group ionic size increase because n increases Across a period the pattern is complex N I Summaw all Seetien III Metallic ibehawiar eerrelav tea wilth large atemie else and law lenizatlen energy Thee metallie hehavier inereaeee dawn a Eireup ane deereaeee aereee a marine Elementa in Greene 1M1 and ENE are atreng reaming agents nenme tala in Esr eeae nl l il and mm are etreng ex idiaing agents Withie the main greuee metal a dea are haeie anal r neemetal exieee aeiele Thea eeidee became mere aeieie agrees a periee and mere baeie ae wm 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