sept 22, 24 notes
sept 22, 24 notes CHEM 1030 - 003
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This 3 page Class Notes was uploaded by Karlee Castleberry on Thursday September 24, 2015. The Class Notes belongs to CHEM 1030 - 003 at Auburn University taught by John D Gorden in Fall 2015. Since its upload, it has received 42 views. For similar materials see Fundamentals Chemistry I in Chemistry at Auburn University.
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Date Created: 09/24/15
Tuesday September 22 2015 Ch 4 Periodic Trends of the Elements 41 Development of the periodic table Newlands every eighth element had similar properties 42 The Modern Periodic Table transition metals are found in group 18 and 3888 group 28 have d subshells and are not transition metals lanthanides and actinides make up fblock transition elements outermost electrons of an atom are valence electrons involved in formation of chemical bonds similarity of valence electron configurations help predict chemical properties for group 1A noble gasns1 classification of elements 43 Effective Nuclear Charge Effective nuclear charge Zeff is the actual magnitude of positive charge that is experienced by an electron in the atom in a multielectron atoms electrons are attracted to nucleus and are repelled by one another results in shielding electron partially shielded from positive charge of the nucleus by other electrons most effective electrons are the core electrons Zeff increases steadily from left to right more powerful positive charge is more negative charge will stick 39 Zeff Z O Z is of protons o is shielding constant Thursday September 24 2015 Zeff increases from left to right across a period but changes very little down a column Example of He Removal of first electron requires less energy than removal of second due to shielding first 1 takes 394 x 103918 to remove second takes J 872 x 103918 second pulled in tighter 44 Periodic Trends in Properties of Elements Atomic radius distance between nucleus and valence shell Atomic Radi 39r rialquot mum quot3quot 139 atomic radius in metals or metallic radius is 12 distance between nuclei of two adjacent identical metal atoms atomic radius in nonmetals covalent radius is 12 the distance between adjacent identical nuclei connected by a chemical bond atomic radius increases from top to bottom down a group highest atomic radii in the very top right of the periodic table decreases from left to right across a period due to increased attraction between effective nuclear charge and charge on valence shell increasing Zeff which draws the valence shell closer to the nucleus F 1 28 ld2 1912d2 2423d2 Thursday September 24 2015 128 is Zeff 1 is charge on valence shell ionization energy how much energy to remove an electron result is an ion a chemical species with a net charge Nag gt Nag e39 sodium has an ionization energy of 4958 kJmol 4958 kJmol is the first ionization energy of sodium IE1Na which corresponds to the removal of the most loosely held electron things that have the same electron configuration are isoelectronic repulsion for half filled as Zeff increases ionization energy increases electrons with a higher value of l are higher in energy thus easier to remove removing a paired electron is easier because of the repulsive forces between 2 electrons in the same orbital Nag gt Nag e39 IE1Na 4958 kJmol easy Nag gt Na2g e39 IE2Na 4562 kJmol more difficult harder to remove an electron from a cation than an atom core electrons have greater Zeff because of fewer filled shells shielding them from the nucleus core electrons closer to nucleus electron affinity energy given off when an electron comes into an atom
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