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Premium member Presentation Transcript Slide 1: THE PERIODIC TABLE AND PERIODIC TRENDS Development of the Periodic Table : Development of the Periodic Table The First Periodic Table Arranged elements by increasing atomic mass Noticed a regular pattern in chemical and physical properties Blank spaces – Predicted the existence of elements not yet discovered based on properties MENDELEEV Slide 4: Determined atomic number of elements by determining nuclear charge CONTD. MOSELY The Modern Periodic Table : The Modern Periodic Table Periods – Horizontal Rows Groups/Families – Vertical Columns Elements in groups have similar physical and chemical properties Periodic Law: When elements are arranged in order of increasing atomic number, there is a regular pattern in their chemical and physical properties Electron Configurations & Periodicity : Electron Configurations & Periodicity Electrons – play a large part in determining physical & chemical properties of elements Arrangements related to position on the table Groups have the same outer orbital configuration in consecutively higher energy levels Periods have outer electrons in the same energy level 4 Classifications : 4 Classifications Noble Gases: elements in which outermost s and p sublevels are filled [full octet of valence e-] Representative (Main Group 1A-7A) elements: outermost s or p sublevels are only partially filled. The number of valence electrons can be determined by the group number Transition Metals – elements in which s and nearby d sublevels contain electrons Inner Transition Metals – elements in which s and nearby f sublevels contain electrons Trends in Atomic Size : Trends in Atomic Size Atomic Radius: half of the distance between the nuclei of two atoms of the same element bonded together. Group Trends: Generally increase as one goes down a group in the periodic table Electrons occupy consecutively higher energy levels, farther from the nucleus Nuclear charge increases, but outermost orbitals are larger due to distance Shielding effect increases with additional number of occupied orbitals between the outermost electrons and the nucleus Atomic Radius Cont. : Atomic Radius Cont. Period Trends: Decreases left to right across the periodic table Electrons are added to the same principle energy level Increased nuclear charge “pulls” them closer to the nucleus Trends in Ionic Size : Trends in Ionic Size Positive ions are smaller than the neutral atoms from which they are formed Electrons are lost from energy levels farthest from the nucleus Remaining electrons pulled closer to the nucleus Negative ions are larger than the neutral atoms from which they are formed Electrons are gained, resulting in smaller effective nuclear charge for the greater number of electrons Repulsive forces between electrons increases across the periods Ionic Size Trends Cont. : Ionic Size Trends Cont. The trends follow the same pattern as atomic size Larger from top to bottom Smaller from left to right Trends in Ionization Energy : Trends in Ionization Energy Ionization Energy: energy needed to remove an electron from a gaseous atom Group 1: easily loses its 1 valence electron Low first ionization energy Second ionization energy will be very high since it is “happy” with losing 1 electron. Group 2: easily lose 2 valence electrons Low first and second ionization energies High third ionization energy Ionization Energy Trends : Ionization Energy Trends Group Trends: decreases from top to bottom on the periodic table Outermost electrons are farther from the effect of the nuclear charge and therefore easier to remove Shielding effect increases down the table Period Trends: increases from left to right Nuclear charge is increasing with no increase in shielding effect Outermost electrons are closer to the nucleus Electron Affinity Trends : Electron Affinity Trends Electron Affinity: energy change that accompanies the addition of an electron to a gaseous atom Most electron affinities are negative because most elements release energy when they become negative ions Group: Decreases from top to bottom Period: Increases left to right Electron Affinity Trends(Same as for Ionization Energy) : Electron Affinity Trends(Same as for Ionization Energy) Group Trends: decreases from top to bottom on the periodic table Outermost electrons are farther from the effect of the nuclear charge and therefore easier to remove Shielding effect increases down the table Period Trends: increases from left to right Nuclear charge is increasing with no increase in shielding effect Outermost electrons are closer to the nucleus Electronegativity : Electronegativity Electronegativity: tendency for an atom to attract electrons to itself when it is chemically combined with another element Group: decreases top to bottom Period: increases left to right Slide 17: Electronegativity Trends(Similar to Ionization Energy) Group Trends: decreases from top to bottom on the periodic table Outermost electrons are farther from the effect of the nuclear charge and therefore more difficult to attract Shielding effect increases down the table Period Trends: increases from left to right Nuclear charge is increasing with no increase in shielding effect Outermost electrons are closer to the nucleus and attracted more easily General Explanations : General Explanations Shielding effect plays a major role in how strongly the nucleus can pull on its outermost electrons – This mainly effects group trends. Nuclear charge is a measure of the strength of a nucleus’ pull - This greatly effects period trends because shielding effect is not an issue across a period. Slide 19: THANK YOU You do not have the permission to view this presentation. In order to view it, please contact the author of the presentation.