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

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

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Decreasing Atomic Size Across 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 Li Be B 1s22s1 1s22s2 1s22s22p1 Li Be B + + + + + + + + + + + +

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

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atomic radius atomic number 0.3 Cs Rb 0.25 K 0.2 Na La Li 0.15 Zn Xe
transition series 4d transition series atomic radius La Li 0.15 Zn Xe Kr 0.1 Cl F 0.05 He H atomic number

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Atomic Radii INCREASES INCREASES 1 2 13 14 15 16 17 Li Na K Rb Cs Cl S
Li Na K Rb Cs Cl S P Si Al Br Se As Ge Ga I Te Sb Sn In Tl Pb Bi Mg Ca Sr Ba Be F O N C B

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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 IONS!!!

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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

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Ionization Energies INCREASES DECREASES Period Be Al Si Ti V Cr Mn Fe
Group 1 18 DECREASES 1 2 3 4 5 6 7 Be 900 Al 578 Si 787 Ti 659 V 651 Cr 653 Mn 717 Fe 762 Co 760 Ni 737 Cu 746 Zn 906 Ga 579 Ge Nb 652 Mo 684 Tc 702 Ag 731 Cd 868 In 558 Sn 709 Sb 834 Ta 761 W 770 Re Hg 1007 Tl 589 Pb 716 Bi 703 N 1402 O 1314 F 1681 Cl 1251 C 1086 S 1000 Br 1140 I 1008 Na 496 K 419 Rb 403 Cs 376 Ba 503 Fr — Ra 509 H 1312 B 801 P 1012 As 947 Se 941 Ru 710 Rh 720 Pd 804 Te 869 Os 839 Ir 878 Pt Au 890 Po 812 At Actinide series Li 520 Ca 590 Sc 633 Sr 550 Y 600 Zr 640 Hf Mg 738 La 538 Ac 490 Lanthanide series 11 12 13 14 15 16 17 9 Ne 2081 Ar 1521 Kr 1351 Xe 1170 Rn 1038 He 2372 Rf Db Sg Bh Hs Mt Ce 534 Pr 527 Nd 533 Pm 536 Sm 545 Eu 547 Gd 592 Tb 566 Dy 573 Ho 581 Er Tm 597 Yb 603 Lu 523 Th 587 Pa 570 U 598 Np Pu 585 Am Cm Bk 601 Cf 608 Es 619 Fm 627 Md 635 No 642 Lr Ds Uub Uut Uuq Uup Uuu Uuo Symbol First Ionization Energy (kJ/mol) 8 10 Period Linus Pauling ( ) awarded Nobel Prize in chemistry in for his 1939 text, The Nature of the Chemical Bond, and also won the Nobel Peace Prize in 1962 for his fight to control nuclear weapons. The greater the electronegativity of an atom in a molecule, the more strongly it attracts the electrons in a covalent bond.

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She’s unhappy and negative.
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”

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

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

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

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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!!!!

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Electron Affinity & Electronegativity
INCREASES DECREASES 1A 8A H 2.1 B 2.0 P As Se 2.4 Ru 2.2 Rh Pd Te Os Ir Pt Au Po At ` 1 1 2A 3A 4A 5A 6A 7A Li 1.0 Be 1.5 Al Si 1.8 Ti V 1.6 Cr Mn Fe Co Ni Cu 1.9 Zn 1.7 Ga Ge Nb Mo Tc Ag Cd In Sn Sb Ta W Re Hg Tl Pb Bi N 3.0 O 3.5 F 4.0 Cl C 2.5 S Br 2.8 I 2 2 Na 0.9 K 0.8 Rb Cs 0.7 Ba Fr Ra Below 1.0 Mg 1.2 3 3 3B 4B 5B 6B 7B 1B 2B Period Ca 1.0 Sc 1.3 4 4 Sr 1.0 Y 1.2 Zr 1.4 5 5 Linus Pauling ( ) awarded Nobel Prize in chemistry in 1954 for his text, The Nature of the Chemical Bond, and also won the Nobel Peace Prize in for his fight to control nuclear weapons. The greater the electronegativity of an atom in a molecule, the more strongly it attracts the electrons in a covalent bond. La 1.1 Hf 1.3 6 6 Ac 1.1 7 Electronegativity Lanthanides: Actinides: Hill, Petrucci, General Chemistry An Integrated Approach 2nd Edition, page 373

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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!

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

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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? QUIZ!!!!!

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