Transcript Atomic Size
Atomic Structure and Chemical Periodicity Atomic Size – Quantum mechanical model doesn’t sharply define boundary to limit size – Atomic radius: ½ the distance between nuclei of 2 like atoms in a diatomic molecule • • Atomic radius Atomic size Atomic Size Increasing Atomic Size “Fatty Francium” Atomic Size Increasing Octet Rule: atoms want 8 e- in their valence energy level Ionization Energies: amount of energy required to remove an electron from the valence shell of an atom Nobel Gases - don’t want to lose e- so they have very high ionization energy Li - doesn’t take much energy to lose e-, low ionization energy F - wants to gain an e- , therefore takes large amount of energy to pull off an e-, high ionization energy Examples • Which atom has the larger radius? –Be or Ba Ba –Ca or Br Ca ▫ As you move down a group the ionization energy decreases b/c of the shielding effect e- ee- e- e- + e- ee- e- Inner e- tend to push outer eaway from the nucleus b/c both have negative charges e- e- ▫ As a result of this shielding effect outer e- are less tightly bound to the nucleus than inner e- D. Ionization Energy (cont.) Ionization Energy Increase Ionization Energy Increase Ionic Size • Ion – positively (cation) or negatively (anion) charged atom, gains or loses electrons Ionic Size Increase Cations Increase Anions Increase Examples • Which atom has the higher ionization energy –N or Bi –Ba or Ne N Ne Electronegativity • The electronegativity of an element is the tendency for the atoms to attract e- when they are chemically combined with another element • Noble Gases have NO electronegativity b/c they don’t gain e• Increase from left to right b/c of octet rule • Decrease when move down a group b/c of shielding effect E. Electronegativity (cont.) Electronegativity Increase Electronegativity Increase F. Summary of Trends Periodic Table of the Elements Atomic Size Increasing Fr “Fatty Francium” Ionic Size Increasing F Electronegativity Increase Atomic Size Increasing Ionization Energy Increase “Friendly Fluorine” Ionization Energy Increase Ionic Size Increasing Electronegativity Increase Whiteboard Practice Which of these elements has a larger atomic size? 1. Li or K 3. Te or I 2. C or O elements in4.order Ca or Arrange these of Kincreasing atomic size. S, Cl, Al, Na Answer: Cl, S, Al, Na Is this a period trend or a group trend? Answer: Period trend White Board Practice Write the element with the greatest value for Ionization Energy. 1. Al or P 3. O or Ne 2. Ca or Ni 4. Zr or Cs Rank the sets of atoms from smallest to largest for Electronegativity. 1. Se, Cr, Zn Cr, Zn, Se 2. P, Ar, Mg Ar, Mg, P Atomic Size War! • Each card has an element symbol. • You will flip over one card and place it on the table and your partner will do the same. • Who ever has the Element with the GREATER atomic size Wins those two elements. • You continue to each flip over cards until one player has all the elements. • If you flip over the same element you will each turn over one more card and the player with the greater atomic size will win all four cards. • Separate the cards and shuffle and play a new game using a different trend.