ChemistryNotesChp4.pdf CHEM 1030-006
Popular in Fundamentals Chemistry 1
verified elite notetaker
Popular in Chemistry
This 3 page Class Notes was uploaded by Emma Karlson on Sunday October 11, 2015. The Class Notes belongs to CHEM 1030-006 at Auburn University taught by Brett A Cagg in Summer 2015. Since its upload, it has received 31 views. For similar materials see Fundamentals Chemistry 1 in Chemistry at Auburn University.
Reviews for ChemistryNotesChp4.pdf
Report this Material
What is Karma?
Karma is the currency of StudySoup.
Date Created: 10/11/15
Chemistry Chapter 4 41 Development of the Periodic Table Law of octaves when the elements are arranged in order of atomic number that every eighth element that similar properties Mendeleev grouped elements according to properties Ordering the periodic table by atomic number instead of atomic mass enabled scientists to make sense of discrepancies Entries today include atomic number and symbol and are arranged according to electron configuration Classification of Elements The main group elements also called the representative elements are the elements in Groups 1A through 7A The noble gases are found in Group 8A and have completely filled p subshells 42 The Modern Periodic Table The transition metals are found in Group 13 and 33 through 8B Group ZB have filled d subshells and are not transition metals The lanthanides and actinides make up the fblock transition elements The outermost electrons of an atom are called the valence electrons o Involved in the formation of chemical bonds Similarity of valence electron configurations helps predict chemical properties 43 Effective Nuclear Charge Effective nuclear charge Zeff is the actual magnitude of positive charge hat is experienced by an electron in the atom In a multielectron atom electrons are simultaneously attracted to the nucleus and repelled by one another 0 The results in shielding where an electron is partially shielded from the positive charge of the nucleus by the other electrons 0 Although all electrons shield one another to some extent the most effective are the core electrons 0 As a result the value of Zeff increases steadily from left to right because the core electrons remain the same but Z increases Effective Nuclear Charge In general the effective nuclear charge is given by Zeff Zo Z is the nuclear charge the number of protons in the nucleus 0 o is the shielding constant Zeff increases from left to right across a period changes very little down a column 44 Periodic Trends in Properties of Elements Atomic radius is the distance between the nucleus of an atom and its valence shell 0 Atomic radius in metals or metallic radius is half the distance between the nuclei of two adjacent identical metal atoms 0 Atomic radius in nonmetals or covalent radius is half the distance between adjacent identical nuclei connected by a chemical bond Atomic Radius The atomic radius increases from top to bottom down a group 0 Increasing n so outermost shell lies farther from the nucleus Atomic radius decreases from left to right across a period 0 Increasing Zeff which draws the valence shell closer to the nucleus Atomic radius decreases left to right across a period due to increased electrostatic attraction between the effective nuclear charge and the charge on the valence shell Ionization Energy Ionization energy IE is the minimum energy required to remove an electron from an atom in the gas phase The result is an ion a chemical species with a net charge NaIg gt Nag e39 In general as Zeff increases ionization energy also increases 0 Thus IE increases from left to right across a period Within a given shell electrons with a higher value of L are higher in energy and thus easier to remove Removing a paired electron is easier because of the repulsive forces between two electrons in the same orbital It is possible to remove additional electrons in subsequent ionizations giving IE1 IE2 and so on It takes more energy to remove the 2nd 3rd 4th etc electrons because it is harder to remove an electron from a cation than an atom It takes much more energy to remove core electrons than valence 0 Core electrons are closer to nucleus 0 Core electrons experience greater Zeff because of fewer filled shells shielding them from the nucleus Electron Affinity Electron affinity EA is the energy released when an atom in the gas phase accepts an electron Clg e gt Clg Like ionization energy electron affinity increases from left to right across a period as Zeff increases 0 Easier to add an electron as the positive charge of the nucleus increases It s easier to add an electron to an s orbital than to add one to a p orbital with the same principal quantum number Within a p subshell it s easier to add an electron to an empty orbital than to add one to an orbital that already contains an electron More than one electron may be added to an atom While many first electron affinities are positive subsequent electron affinities are always negative o Considerable energy is required to overcome the repulsive forces between the electron and the negatively charged ion Metallic Character Metals tend to 0 Be shiny lustrous malleable and ductile 0 Be good conductors of both heat and electricity 0 Have low ionization energies commonly form cations Nonmetals tend to o Vary in color and are not shiny 0 Be brittle rather than malleable 0 Be poor conductors of both heat and electricity 0 Have high electron affinities commonly form anions Metalloids are elements with properties intermediate between those of metals and nonmetals Coulomb s law F Q1xQ2d2 45 Electron Configurations of Ions To write the electron configuration of an ion formed by a main group element 0 1 Write the configuration for the atom o 2 Add or remove the appropriate number of electrons Ions of Main Group Elements Species with identical electron configurations to the noble gas to the right are called isoelectronic Common monatomic ions arranged by their positions in the periodic table Ions of dblock Elements Removing electrons first form the shell with the highest value of n forms ions of dblock elements For Fe to Fe two electrons are lost from the 4s subshell not the 3d 46 Ionic Radius The ionic radius is the radius of a cation or an anion When an atom loses an electron to become a cation its radius decreases due in part to a reduction in electronelectron repulsions in the valence shell A significant decrease in radius occurs when all of an atom s valence electrons are removed Comparing Ionic Radius with Atomic Radius When an atom gains one or more electrons and becomes an anion its radius increases due to increased electronelectron repulsion Isoelectronic Series An isoelectronic series is a series of 2 or more species that have identical electron configurations but different nuclear charges