1. Trends & the Periodic Table

2. Trends More than 20 properties change in predictable way based on location of elements in PTMore than 20 properties change in predictable way based on location of elements in PT Ex: density, melting point, atomic radius, ionization energy, electronegativityEx: density, melting point, atomic radius, ionization energy, electronegativity

3. Atomic radiusAtomic radius Ionization energyIonization energy ElectronegativityElectronegativity

4. Atomic Radius Atomic radius = 1/2 distance between neighboring nuclei in molecule or crystalAtomic radius = 1/2 distance between neighboring nuclei in molecule or crystal “size” varies bit from substance to substance“size” varies bit from substance to substance

5. Cannot measure electron cloud: X-ray diffraction pinpoints nuclei to measure distance

6. Trends: Atoms get larger as go down a column – ↑ principal energy levels

7. 2-8-18-32-18-8-1Fr7 2-8-18-18-8-1Cs6 2-8-18-8-1Rb5 2-8-8-1K4 2-8-1Na3 2-1Li2 1H1 ConfigurationElementPeriod Going down column 1: ↑ energy levels as go down, so makes sense that atoms get larger makes sense that atoms get larger

8. previousprevious | index | nextindexnext Li: Group 1 Period 2 Cs: Group 1 Period 6

9. 2-8NeVIIIA or 18 2-7FVIIA or 17 2-6OVIA or 16 2-5NVA or 15 2-4CIVA or 14 2-3BIIIA or 13 2-2BeIIA or 2 2-1LiIA or 1 ConfigurationElementFamily Going across row 2: You are still adding electrons – shouldn’t they get larger?!Atoms actually get a bit smaller as you go across a row What’s going on? You are still adding electrons – shouldn’t they get larger?! Atoms actually get a bit smaller as you go across a row What’s going on?

10. What do you remember about charge? opposites attract/like charges repelopposites attract/like charges repel valence electrons are pulled into atom by (+) charge of nucleusvalence electrons are pulled into atom by (+) charge of nucleus the greater the (+) charge, the more pulling powerthe greater the (+) charge, the more pulling power

11. as go L to R across row the size ↓ a bit because of greater “proton pulling power (PPP)” previousprevious | index | nextindexnext

12. size  as you go  & size  as you go  previousprevious | index | nextindexnext

13. Ionization Energy amount energy required to remove electron from an atomamount energy required to remove electron from an atom Ionization energy = energy required to remove most loosely held valence electronIonization energy = energy required to remove most loosely held valence electron

14. Trends in ionization energy What do you think happens to the ionization energy as you go down a column of the periodic table?What do you think happens to the ionization energy as you go down a column of the periodic table? As you go across a row?As you go across a row?

15. Same group: Cs’ valence electron farther away from nucleus so electrostatic attraction is much weaker (easier to steal electron away from Cs) previousprevious | index | nextindexnext

16. Same row: easier to steal electron from Li than Ne easier to steal electron from Li than Ne Li: less PPP than Ne Li: less PPP than Ne previousprevious | index | nextindexnext

17. Trends in ionization energy Ionization energy ↓ as go down columnIonization energy ↓ as go down column – easier to remove valence electron as gets farther away (↑ # electron levels) – easier to remove valence electron as gets farther away (↑ # electron levels) Ionization energy ↑ as go across rowIonization energy ↑ as go across row – it’s more difficult to remove valence electron due to ↑ PPP – it’s more difficult to remove valence electron due to ↑ PPP

18. Electronegativity Ability of atom to attract electrons in a bondAbility of atom to attract electrons in a bond Noble gases do not form bondsNoble gases do not form bonds –are inactive –don’t have electronegativity values Unit = PaulingUnit = Pauling –Fluorine: most electronegative element (4.0 Paulings)

19. Trends in electronegativity Related to “proton pulling power (PPP)”Related to “proton pulling power (PPP)” ↑left to right across a row↑left to right across a row ↓top to bottom of a column↓top to bottom of a column

20. Electronegativity increases in direction of arrow from Fr towards F (most electronegative element)

21. Reactivity of Metals metals are losers!metals are losers! judge reactivity of metals by how easily theyelectronsjudge reactivity of metals by how easily they give up electrons most active metals: Fr (#1) and Cs (#2)most active metals: Fr (#1) and Cs (#2) Reactivity metals: ↑ as ionization energy ↓Reactivity metals: ↑ as ionization energy ↓

22. Trends for Reactivity of Metals (AKA: Metallic Character) Increases as go down columnIncreases as go down column –Easier to lose electrons! Decreases as go across rowDecreases as go across row –Harder to lose electrons!

23. Reactivity of Non-metals non-metals are winners!non-metals are winners! judge reactivity of non-metals by how easily theyelectronsjudge reactivity of non-metals by how easily they gain electrons most active non-metal: fluorinemost active non-metal: fluorine reactivity non-metals: ↑ as electronegativity ↑reactivity non-metals: ↑ as electronegativity ↑

24. Trend for Reactivity of Non-metals depends on PPP ↑ as go across row (left to right)↑ as go across row (left to right) ↓ as go down column (top to bottom)↓ as go down column (top to bottom) –shielded by more inner-shell electrons

25. Ionic Size Relative to Parent Atom Depends on if (+) ion or (-) ionDepends on if (+) ion or (-) ion How do you create a positive ion?How do you create a positive ion? How do you create a negative ion?How do you create a negative ion? Remove electrons Add electrons

26. How do you know if an atom gains or loses electrons? Octet rule: magic # 8 Metals have 1, 2, or 3 valence electronsMetals have 1, 2, or 3 valence electrons –easier to lose them Nonmetals have 5, 6, or 7 valence electronsNonmetals have 5, 6, or 7 valence electrons –easier to gain more Noble gases: have 8 so don’t form ionsNoble gases: have 8 so don’t form ions

27. Positive ions or cations Cations always smaller than parent atomCations always smaller than parent atom –lost electrons therefore smaller in size

28. Negative ions or anions Anions always larger than parent atomAnions always larger than parent atom –gained electrons therefore larger in size