lecture4 (10-6-2006) Ch 2-3

lecture4 (10-6-2006) Ch 2-3 - Group 1A – Alkali metals(Li...

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Unformatted text preview: Group 1A – Alkali metals (Li, Na, K, etc.) Group 2A – Alkaline Earth metals (Be, Mg, Ca, etc.) Group 7A – Halogen (F, Cl, Br, I, etc.) Group 8A – Inert (noble or rare) gases (He, Ne, Ar, Kr, Xe, etc.) Important observation : Inert gases He, Ne, Ar, Kr, and Xe have 2, 10, 18, 36, and 54 electrons are extra-stable. Properties and bonding of atoms depends on the electron arrangement or electron configurations Chemistry 2A Chemistry 2A-c F2006 c F2006 (Ch2 (Ch2-13) 13) The alkali metals tend to form cations with a +1 charge and the halogens tend to form anion with a –1 charge in chemical reactions. Example : 2Na(s) + Cl 2 (g) → 2NaCl(s) [=(Na + )(Cl- )] Half –reactions: Na → Na + + e- Cl + e- → Cl- Ionic bond Exist as Li + , Na + , K + in compounds Exist as Be 2+ , Mg 2+ , Ca 2+ in compounds Exist as F- , Cl- , Br- in compounds Na (11 p’s + 11 e- ‘s) Na + (11 p’s + 10 e- ‘s) Mg (12 p’s + 12 e- ‘s) Mg ++ (11 p’s + 10 e- ‘s) O (8 p’s + 8 e- ‘s) O 2- (8 p’s + 10 e- ‘s) Cl (17 p’s + 17 e- ‘s) Cl- (17 p’s + 18 e- ‘s) Ionic Compounds: MgCl 2 = (Mg ++ )(2Cl- ) MgO = (Mg ++ )(O 2- ) Same # of electrons as in Ne Same # of electrons as in Ar Chemistry 2A Chemistry 2A-c F2006 c F2006 (Ch2 (Ch2-14) 14) VII. Mole and the Avogadro Number A mole of substance contains the Avogadro’s number of elementary entities The # of 12 C atoms in exactly 12 g of...
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lecture4 (10-6-2006) Ch 2-3 - Group 1A – Alkali metals(Li...

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