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Periodic Trends

Periodic Trends

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Periodic Trends

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  1. Periodic Trends • There are several important atomic characteristics that show predictable trends that you should know: • Atomic Size • Ionization Energy • Electron Affinity • Electronegativity

  2. Atomic Size The bonding atomic radius is defined as one-half of the distance between bonded nuclei.

  3. Decreasing Atomic SizeAcross a Period • The effect is that the more positive nucleus (+) has a greater pull on the electron cloud (-) • The increased attraction pulls the cloud in, making atoms smaller as we move from left to right across a period Be B Li 1s22s1 1s22s2 1s22s22p1 Li Be B + + + + + + + + + + + +

  4. Relative Size of Atoms Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 350

  5. 0.3 Cs Rb 0.25 K 0.2 Na 4d transition series 3d transition series La atomic radius Li 0.15 Zn Xe Kr 0.1 Cl F 0.05 He H 0 0 10 20 30 40 50 60 atomic number

  6. INCREASES Li Be C N O B F 0.88 0.77 0.70 0.66 0.64 1.52 1.11 Na Mg Al Si P S Cl 1.86 1.60 1.43 1.17 1.10 1.04 0.99 INCREASES K Ca Ge As Se Br Ga 2.31 1.97 1.22 1.22 1.21 1.17 1.14 Rb Sr In Sn Sb Te I 1.62 1.40 1.41 1.37 1.33 2.44 2.15 Cs Ba Pb Tl Bi 2.62 2.17 1.71 1.75 1.46 Atomic Radii 1 2 13 14 15 16 17

  7. IONS!!! Ionization Energy Amount of energy required to remove an electron from the ground state of a gaseous atom or ion. Given enough energy (in the form of a photon) an electron can leave the atom completely. The number of protons and electrons is no longer equal

  8. Ionization Energy • Generally, as one goes across a row, it gets harder to remove an electron. • The larger the atom is, the easier its electrons are to remove. • Ionization energy and atomic radius are inversely proportional

  9. H 1312 He 2372 Symbol First Ionization Energy (kJ/mol)‏ Mg 738 1 1 13 15 17 2 14 16 Li 520 Be 900 B 801 C 1086 N 1402 O 1314 F 1681 Ne 2081 2 2 DECREASES Na 496 Mg 738 Al 578 Si 787 P 1012 S 1000 Cl 1251 Ar 1521 3 3 12 4 6 8 9 10 11 3 5 7 K 419 Ca 590 Sc 633 Ti 659 V 651 Cr 653 Mn 717 Fe 762 Co 760 Ni 737 Cu 746 Zn 906 Ga 579 Ge 762 As 947 Se 941 Br 1140 Kr 1351 4 4 Rb 403 Sr 550 Y 600 Zr 640 Nb 652 Mo 684 Tc 702 Ru 710 Rh 720 Pd 804 Ag 731 Cd 868 In 558 Sn 709 Sb 834 Te 869 I 1008 Xe 1170 5 5  Cs 376 Ba 503 La 538 Hf 659 Ta 761 W 770 Re 760 Os 839 Ir 878 Pt 868 Au 890 Hg 1007 Tl 589 Pb 716 Bi 703 Po 812 At -- Rn 1038 6 6  Uuu -- Uub -- Uut -- Uuq -- Uup -- Uuo -- Fr -- Ra 509 Ac 490 Rf -- Db -- Sg -- Bh -- Hs -- Mt -- Ds -- 7  Ce 534 Pr 527 Nd 533 Pm 536 Sm 545 Eu 547 Gd 592 Tb 566 Dy 573 Ho 581 Er 589 Tm 597 Yb 603 Lu 523 Lanthanide series  Th 587 Pa 570 U 598 Np 600 Pu 585 Am 578 Cm 581 Bk 601 Cf 608 Es 619 Fm 627 Md 635 No 642 Lr -- Actinide series Ionization Energies INCREASES 18 Group 1 Period

  10. + + Ions • Here is a simple way to remember which is the cation and which the anion: This is Ann Ion. This is a cat-ion. She’s unhappy and negative. Cats are “paw-sitive”

  11. Sizes of Ions • Cations are smaller than their parent atoms. • The outermost electron is removed and repulsions are reduced.

  12. Sizes of Ions • Anions are larger than their parent atoms. • Electrons are added and repulsions are increased.

  13. Electron Affinity Electron affinity=“Love” of electrons Energy change accompanying addition of electron to gaseous atom: Cl + e− Cl−

  14. Electronegativity • Electronegativity is a measure of an atom’s attraction for another atom’s electrons. • Is directly related to Electron Affinity • scale that ranges from 0 to 4. • Fluorine is the most electronegative!!!!

  15. H 2.1 Be 1.5 B 2.0 C 2.5 N 3.0 O 3.5 F 4.0 Na 0.9 Al 1.5 Si 1.8 P 2.1 S 2.5 Cl 3.0 DECREASES K 0.8 Ti 1.5 V 1.6 Cr 1.6 Mn 1.5 Fe 1.8 Co 1.8 Ni 1.8 Cu 1.9 Zn 1.7 Ga 1.6 Ge 1.8 As 2.0 Se 2.4 Br 2.8 Rb 0.8 Nb 1.6 Mo 1.8 Tc 1.9 Ru 2.2 Rh 2.2 Pd 2.2 Ag 1.9 Cd 1.7 In 1.7 Sn 1.8 Sb 1.9 Te 2.1 I 2.5 Cs 0.7 Ba 0.9 Ta 1.5 W 1.7 Re 1.9 Os 2.2 Ir 2.2 Pt 2.2 Au 2.4 Hg 1.9 Tl 1.8 Pb 1.8 Bi 1.9 Po 2.0 At 2.2 Fr 0.7 Ra 0.9 Below 1.0 2.0 - 2.4 2.5 - 2.9 1.5 - 1.9 3.0 - 4.0 Electron Affinity & Electronegativity INCREASES 1A 8A ` 1 1 3A 5A 7A 2A 4A 6A Li 1.0 2 2 Mg 1.2 3 3 2B 4B 6B 1B 3B 5B 7B Period Ca 1.0 Sc 1.3 4 4 Sr 1.0 Y 1.2 Zr 1.4 5 5  La 1.1 Hf 1.3 6 6  Ac 1.1  7 Electronegativity  1.0 - 1.4 Lanthanides: 1.1 - 1.3 Actinides: 1.3 - 1.5 Hill, Petrucci, General Chemistry An Integrated Approach 2nd Edition, page 373

  16. Periodic Trends • Atomic Radii - size • Ionization Energy – energy change when losing an e- • Electron Affinity - energy change when gaining an e- • Electronegativity – ability to attract e- when in a compound Forms cation! Forms anion!

  17. Summary of Periodic Trends Atomic radius decreases Ionization energy increases Electron affinity increases Electronegativity increases Atomic radius increases Ionization energy decreases Electron Affinity decreases Electronegativity decreases 1A 0 2A 3A 4A 6A 7A 5A Ionic size (cations) Ionic size (anions)‏ decreases decreases

  18. What ion will be formed when K loses 1 e-? K1+ (cation) • What ion will be formed when O gains 2 e-? O2- (anion) • Which ion above is more electronegative? O2- (anion) QUIZ!!!!!