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The Periodicities of the Periodic Table Ionization energy • energy needed to make an ion by losing electrons First Ionization Energy • Definition: – energy needed to remove the most loosely held e- Valence electron high E electron Outermost electron 1st Why 1st? Is there a 2nd? • 2nd ionization energy –Energy needed to remove the second electron • 3rd ionization energy –Energy needed to remove the third electron 1st 3rd e- removed 2nd e- removed What’s holding the e- in place? • PROTONS • “Opposites attract” • There is a force of attraction between protons (+) and electrons (-) Ionization E trend? • As move across a period…IE increases. WHY? 3 p+ 9 p+ • As you go across a period –a proton and an electron are being added – more p+ hold the e- tighter when in the same energy level • Increasing nuclear charge • As move UP a group … IE increases. WHY? Period 1 More E to remove Period 2 Period 3 Period 4 Let’s figure it out . . . Potassium 19 p+ Sodium 11 p+ Lithium 3 p+ INCREASES because ... • As you go up a group –the electron shells get closer to the nucleus and can hold on to the e- tighter. –ALSO…………………. Potassium 19 p+ SHIELDING • as you go DOWN a group – Not only does the distance increase between the p+ and valence e• e- in outer shells repel each other & makes them easier to remove Who has the highest IEs? Lowest? Electronegativity E-neg Electronegativity • Ability of an atom to attract electrons of other atoms. • In other words. . . – Atoms with high e-neg are bullies that steal electrons Electronegativity • Periodic trend F INCREASES EXCEPT for Noble gases. WHY? Already have full valence shell! Summary Atoms with high electronegativities also have high ionization E Atomic Radius • Radius –distance from the center of a circle (Nucleus) to the outermost edge (valence shell) R Atomic Radius Periodicity D E C R E A S E S DECREASES Why????? • Why does atomic radius DECREASE as you move up a group? • Losing full Energy levels • Why does atomic radius DECREASE as you move across a period? • Increasing the # of p+ holds the ein tighter NOW Compare • the radii of Na0 and Na+ • POSITIVE Ionic radius is smaller • the radii of Cl0 and Cl• NEGATIVE Ionic radius is larger Compare 2 different elements • Compare the ionic radius of Mg2+ and the atomic radius of Ne. The ionic radius of Mg2+ is smaller than the atomic radius of Ne because the Mg 2+ ion has more p+ (12) than the Ne atom (10). General Formulas of compounds • You can look at the groups on the periodic table and determine how they will combine with elements of different groups. • Group 1 Group 2 Group16 Group 17 • +1 +2 -2 -1 1:1 General Formula: AB • Group 1 Group 2 Group16 Group 17 • +1 +2 -2 -1 1:1 General Formula: AB • Group 1 Group 2 Group16 Group 17 • +1 +2 -2 -1 2:1 General Formula: A2B • Group 1 Group 2 Group16 Group 17 • +1 +2 -2 -1 1:2 General Formula: AB2 THE END