1. Unit 4: The Periodic Table and Periodic Trends (Periodicity) Chemistry

2. atomic number Background on the Periodic Table Dmitri Mendeleev: given credit for Periodic Table (~1870) -- organized Table by increasing atomic mass left spaces and predicted properties of undiscovered elements put elements in order of increasing ______________. Mendeleev

3. Regions of the Table metals: left side of Table(1-3 valence e-); form cations properties: lustrous (shiny) ductile (can pull into wire) malleable (can hammer into shape) good conductors (heat and electricity) hard

4. nonmetals: right side of Table(5-7 valence e- ; form anions by gaining electrons properties: good insulators, poor conductors gases or brittle solids dull Regions of the Table (cont.) Br 2 I2I2 S8S8 Ne bromineiodinesulfurneon

5. computer chips metalloids (semimetals): “stair” between metals and nonmetals properties: (intermediate)in-between those of metals and nonmetals; “semiconductors” Regions of the Table (cont.) (B, Si, Ge, As, Sb, Te, At) Si and Ge computer chips metals nonmetals

6. Periodicity there are trends in properties of elements -- left-right AND up-down trends atomic radius: the size of a neutral atom add a new energy level each time WHY? …increases as we go …decreases as we go WHY? Increase in nuclear charge it has to do with…

7. Atomic Radii Li Na K Rb Cs Cl S P Si Al Br Se As Ge Ga I Te SbSn In Tl Pb Bi Mg Ca Sr Ba Be F O N C B 1.52 1.11 1.86 1.60 2.31 1.97 2.44 2.15 2.62 2.17 0.88 0.77 0.70 0.66 0.64 1.43 1.17 1.10 1.04 0.99 1.22 1.22 1.21 1.17 1.14 1.62 1.40 1.41 1.37 1.33 1.71 1.75 1.46 IA IIA IIIA IVA VA VIA VIIA = 1 Angstrom

8. ionic radius: cationsanions Ca atomCa 2+ ion Cl atom Cl 1– ion the size of an ion 20 p + 20 e – 20 p + 18 e – 17 p + 17 e – 17 p + 18 e – Ca Ca 2+ Cl Cl 1– cations lose electrons- smaller Anions gain electrons larger

9. IA IIA IIIA IVA VA VIA VIIA 0.60 0.31 0.95 0.65 1.33 0.99 1.48 1.13 1.69 1.35 1.71 1.40 1.36 0.50 1.84 1.81 0.62 1.98 1.85 0.81 2.21 2.16 0.95 Li 1+ Be 2+ Na 1+ Mg 2+ Cl 1- N 3- O 2- F 1- S 2- Se 2- Br 1- Te 2- I 1- Al 3+ Ga 3+ In 3+ Tl 3+ Ca 2+ K 1+ Sr 2+ Rb 1+ Cs 1+ Ba 2+ Li Na K Rb Cs Cl S P Si Al Br Se As Ge Ga I Te SbSn In Tl Pb Bi Mg Ca Sr Ba 1.52 1.11 1.86 1.60 2.31 1.97 2.44 2.15 2.62 2.17 0.88 0.77 0.70 0.66 0.64 1.43 1.17 1.10 1.04 0.99 1.22 1.22 1.21 1.17 1.14 1.62 1.40 1.41 1.37 1.33 1.71 1.75 1.46 BeBCNOF = 1 Angstrom Atomic Radii Ionic Radii Cations: smaller than parent atoms Anions: LARGER than parent atoms

10. ionization energy: the energy required to remove an e – from an atom As we go, 1st I.E…. Nonmetals tend to gain therefore having a high first ionization energy. Metals tend to lose-low first ionization energy decreases. increases. (due to the shielding effect- increase in the number of energy levels) Each successive ionization requires more energy than the previous one.

11. electronegativity: the tendency for a bonded atom to attract e – to itself As we go, electronegativity… decreases. increases. electronegativity increases Nonmetals tend to gain therefore having a high electronegativity. Metals tend to lose-low electronegativity

12. Reactivity of Metals Increases down a column –Reasons: Size (value of n), low ionization energy, and the shielding effect Decreases left to right across a period –Reasons: Stronger nuclear charge and Increase in ionization energy

13. Reactivity of Nonmetals Increases left to right across a period –Why? Smaller in size Stronger nuclear charge Increased ionization energy Decreases down a column –Why? Decreased electronegativity Larger in size

14. Reactivity Overview Fr-most reactive metal F-most reactive nonmetal Exception: Elements with half- filled sublevels are more stable than those with empty orbitals