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The period table the lowest ionization energy the the

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Unformatted text preview: nergy The The highest electron affinity The Ionic Bond Formation Formation of Ionic Compounds are very exothermic exothermic reactions! ∆H < 0 2Na(s) + Cl2 (g) → 2 NaCl(s) ∆H o = - 410.9kJ/mole f Heat of formation of an ionic compound is very negative Mainly due to lattice energy Lattice Lattice energy Lattice energy : The energy required to completely separate 1 mole of a solid ionic compound into gaseous ions. NaCl(s) → Na + (g) + Cl- (g) ∆H lattice = +788 kJ/mole Endothermic Because the ions are strongly attracted to one another in the lattice. Lattice Energy (Electrostatic Attraction) Lattice energy (E): much depends on the charges of charges ions, the sizes of ions and their arrangement in solid sizes arrangement Q+ : the charge on the cation Q+ ⋅ Q− E=k r Q- : the charge on the anion r : the distance between the ions Compound Lattice energy (E) lattice energy MgF2 MgO 2957 LiF LiCl 1036 853 3938 Q= +2,-1 Q= +2,-2 increases as Q increase increases as r decreases r(F) < r(Cl) Lattice Energy ↓ ↓ ↓ ↓ Larger ion, less lattice lattice energy higher charge, higher lattice energy The The Covalent bond • Covalent bond: the force that holds two atoms together as both nuclei are attracting the same pair of valence nuclei same electrons. “Shared” the pair of valence electrons by the two two atoms-- “octet” F 7e- + F FF 7e- 8e- 8e- share 1 pair of e (2e) single bond (—) Cl - Cl share 2 pairs of e (4e) double bond (=) O=O share 3 pairs of e (6e) triple bond (≡) N≡N The The Covalent bond--- Bond length bond--- Bond length: length: single bond (—) is the longest the Bond strength: triple bond (≡) is the strongest Polar Covalent Bond Polar covalent bond (or polar bond): a covalent bond with greater electron density around one of the two atoms electron poo...
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