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Periodicity

Periodicity. Topic 3 Review Oxford p. 12-14 Text CH 7. General information. Atoms are arranged in order of increasing atomic number Row=Period Elements in the same period have valence electrons in the same outer shell Column = Group or Family Number representative groups 1-8

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Periodicity

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  1. Periodicity Topic 3 Review Oxford p. 12-14 Text CH 7

  2. General information • Atoms are arranged in order of increasing atomic number • Row=Period • Elements in the same period have valence electrons in the same outer shell • Column = Group or Family • Number representative groups 1-8 • Elements in the same group have the same # of valence electrons • Label Alkali Metals, Halogens, Noble Gases • Electron Configuration Patterns • Electron Stuctures for elements 1-20 • Blocks • Label 1s, 2s, etc.

  3. Periodicity • Elements in the same group have similar chemical and physical properties • There is a change in chemical and physical properties across a period. • The repeating pattern of physical and chemical properties is called PERIODICITY • Atomic Radius • Ionic Radius • Ionization Energy • Electronegativity • Melting Point

  4. Atomic Radius • Distance from the nucleus of an atom to it’s outermost electron • Half the distance between the nuclei of two bonded atoms of the same element

  5. Ionic Radius • Cation • Positive ion • Electrons have been lost • Smaller than parent atom • Anion • Negative ion • Electrons have been gained • Bigger than parent atom

  6. Ionization Energy • Energy required to remove an electron from a gaseous atom

  7. Electronegativity • Relative measure of the attraction that an atom has for a shared pair of electrons when covalently bonded to another atom.. • How much an atom likes to take on extra electrons

  8. Nuclear Charge Nuclear Shielding Inner level electrons shield outer level electrons from the pull of the nucleus • The power of the nucleus…the more protons in the nucleus, the great the pull on electrons

  9. Graphing Assignment • Atomic radius • The trend in Atomic Radius going down Group (Column) 1—The Alkali Metals • The trend in Atomic radius across the third period • Ionic Radius • The trend in Ionic radius going down Group (Column) 1—The Alkali Metals • The trend in Ionic Radius across the third period • Ionization Energy • The trend in Ionization Energy going down Group (Column) 8—The Noble Gases • The trend in Ionization Energy across the third period • Electronegativity • The trend in Electronegativity going down Group (Column) 7—The Halogens • The trend in Electronegativity across the third period Melting points • The trend in Melting Points going down Group (Column) 7—The Halogens • The trend in Melting Points across the third period

  10. Graphing Assignment • Each graph needs • Title • Labeled axes • Appropriate range so that graph is spread out • Below the graph make a statement about the trend that describes it and explains it. • Atomic radius decreases across Period 3. As you go across the row, the nuclear charge increases by one proton, while electrons are being added to the third energy level. Each consecutive nucleus pulls the electrons in tighter and tighter

  11. Group 1--Alkali Metals—Li, Na, K, Rb, Cs • Properties • Soft • Malleable • Low melting points • Low densities • Weak metallic bonding (one mobile electron per atom) • Large atoms • Attractions between the nucleus and the outer level electrons decrease down the group as a result an increase in the size of the atom ( nuclear shielding)

  12. Alkali Metals—Chemical Reactivity • Very chemically reactive • Tarnish (oxidize) rapidly in air • Stored under wax to stabilize • One valence electron • Easily lost • Low ionization energies • Low electronegativities • Form 1+ metal ions • Form ionic compounds with reactive non-metals • Oxygen 4Li (s) + O2 (g)  2Li2O (s) • Chlorine 2Na (s) + Cl2 (g)  2NaCl (s) • Bromine 2K (s) + Br2 (g)  2KBr (s) • Iodine 2Cs (s) + I2 (g)  2CsI (s)

  13. Alkali Metals—Chemical reactivity (cont’d) • Called alkali metals because they all react with water to form a basic (alkali) solution • 2M (s) + 2H2O (l)  2M1+ (aq) + 2OH-1 (aq) H2 (g) • 2Li (s) + 2H2O (l)  2Li1+ (aq) + 2OH-1 (aq) H2 (g) • 2K(s) + 2H2O (l)  2K1+ (aq) + 2OH-1 (aq) H2 (g) Li—slow and steady Na—vigorous and fizzy K—violent and ignites • Reactivity increases down the group • Atomic radius increases • Ionic radius increases • Ionization energy decreases • Electronegativity decreases http://www.youtube.com/watch?v=QSZ-3wScePM

  14. Group 7--Halogens—F, Cl, Br, I • Properties • Reactive non-metals • Diatomic Molecules F2, Cl2, Br2, I2 • Atoms joined by one covalent bond • Phases at room temperature • F2 and Cl2 are gases • Br2 is a liquid, • I2 is a solid • Increase in Van der Waal’s forces

  15. Halogens—Chemical reactivity • Very chemically reactive • Seven valence electrons • Easily gain 1 electron • Good oxidizing agents • High ionization energy • High electronegativity • Form 1- “halide ions” • Combine with metals to give ionically bonded salts2Na (s) + Cl2(g)  2NaCl (s) 2K (s) + Br2 (g)  2KBr (s) Ca (s) + F2 (g)  2CaF2 (s) Pb (s) + I2 (g)  2PbI2 (s) Ionic salts are usually soluble in water. Notable exceptions include those that contain lead or silver

  16. Halogens- Reactivity Trends • Reactivity decreases down the group • Atomic radius increases as a new shell is added • Ionic radius increases • Valence electrons become further and further from the nucleus • Increased nuclear shielding prevents the nucleus from being able to attract electrons as strongly as you move down the group. • Ionization energy decreases • Electronegativity decreases

  17. Halogens- Reactivity Trends (cont’d) • Halogens react with halide solutions • Cl2 (g) + 2NaBr Br2 (aq) + 2NaCl (aq) • Cl2 (g) + 2KI (aq)  I2 + 2KCl (aq) • Br2 (g) + 2KI (aq)  I2 (aq) + 2KBr (aq) • Test for Halide Ions F1-, Cl1-, Br1-, I1- • Adding silver nitrate to a halide solution results in the formation of an insoluble silver halide precipitate. • AgNO3 (aq) + NaCL (aq)  NaNO3 (aq) + AgCL (white solid) • AgNO3 (aq) + NaBr (aq)  NaNO3 (aq) + AgBr (cream solid) • AgNo3 (aq) + NaI (aq)  NaNO3 (aq)  NaNO3 (aq) + AgI (yellow solid)

  18. Metals Nonmetals • Dull, brittle, or gases • Non-conductors • P, S, Cl, Ar • Shiny • Good conductors of heat and electricity • Na, Mg, Al

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