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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.
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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 Increasing “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 • Ca or Br • Ba • Ca
e- e- e- e- e- e- + e- e- e- e- e- • As you move down a group the ionization energy decreases b/c of the shielding effect 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-
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
Atomic Size Increasing Ionic Size Increasing F. Summary of Trends “Friendly Fluorine” Electronegativity Increase F Ionization Energy Increase Periodic Table of the Elements Ionic Size Increasing Atomic Size Increasing Electronegativity Increase Ionization Energy Increase Fr “Fatty Francium”
Whiteboard Practice 1. Li or K 3. Te or I 2. C or O 4. Ca or K 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
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 3. O or Ne 2. Ca or Ni 4. Zr or Cs 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.
