Chemical Periodicity Atomic Structure and

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 Atomic Size Increasing “Fatty Francium”

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

Which atom has the larger radius? –BeorBa –CaorBr Ba Ca Examples

▫As you move down a group the ionization energy decreases b/c of the shielding effect e-e- e-e- + e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- Inner e- tend to push outer e- away from the nucleus b/c both have negative charges ▫As a result of this shielding effect outer e - are less tightly bound to the nucleus than inner e -

Ionization Energy Increase D. Ionization Energy (cont.)

Ion – positively (cation) or negatively (anion) charged atom, gains or loses electrons Ionic Size

Cations Increase Ionic Size Increase Anions Increase

Which atom has the higher ionization energy –NorBi –BaorNe N Examples 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

Electronegativity Increase E. Electronegativity (cont.)

Periodic Table of the Elements Atomic Size Increasing Ionic Size Increasing “Fatty Francium” Fr F. Summary of Trends Ionization Energy Increase Electronegativity Increase F “Friendly Fluorine”

Whiteboard Practice Which of these elements has a larger atomic size? Arrange these elements in order of increasing atomic size. S, Cl, Al, Na Answer: Cl, S, Al, Na Is this a period trend or a group trend? Answer: Period trend 1. Li or K 2. C or O4. Ca or K 3. Te or I

White Board Practice Write the element with the greatest value for Ionization Energy. Rank the sets of atoms from smallest to largest for Electronegativity. 1. Al or P 2. Ca or Ni 3. O or Ne 4. Zr or Cs 1. Se, Cr, ZnCr, Zn, Se 2. P, Ar, MgAr, 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.