2na(s) + cl 2 (g) 2nacl (s)
DESCRIPTION
Synthesizing an Ionic Compound. 2Na(s) + Cl 2 (g) 2NaCl (s). Explaining Salt Formation using the Born-Haber Cycle. Explaining Salt Formation using the Born-Haber Cycle. Na(s) + Cl 2 NaCl H° f = -411 kJ/mol. Na(s) Na(g) H° f = 108 kJ/mol. - PowerPoint PPT PresentationTRANSCRIPT
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2Na(s) + Cl2Na(s) + Cl22 (g) (g) 2NaCl (s) 2NaCl (s)
Synthesizing an Synthesizing an IonicIonic Compound Compound
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Explaining Salt Formation using the Explaining Salt Formation using the Born-HaberBorn-Haber Cycle Cycle
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Na(s) + Cl2 NaCl H°f = -411 kJ/mol
Na(s) Na(g) H°f = 108 kJ/mol
Cl2 Cl(g) H°f = 122 kJ/mol
Na(g) Na+(g) + e- I1 = 496 kJ/mol
Cl(g) + e- Cl-(g) E = -349 kJ/mol
H = [H°f (NaCl)] - [H°f (Na+) + H°f (Cl-) + I1 + E]
H = -788 kJ/mol
Explaining Salt Formation using the Explaining Salt Formation using the Born-HaberBorn-Haber Cycle Cycle
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Describing Electrostatic Attraction and Repulsion
E = kQ1Q2
d
E > 0 if the charges Q1 and Q2 have the same sign•Potential energy increases because the particles are repelling
E < 0 if the charges Q1 and Q2 have different signs•Potential energy decreases because the particles are attracting
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The lattice energy of NaCl is the result of all the electrostatic repulsions and attractions. Because the attractions outweigh the repulsions, the lattice energy is positive and large
E = kQ1Q2
d
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Sizes of Ions•size depends upon nuclear charge
•size depends upon numbers of electrons•size depends upon orbitals in which the outer electrons reside
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Within an Isoelectric Series, the higher the atomic numberthe smaller the ion
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Covalent Bonds are formed by shared pairs of electrons
H H+ H H H H
Cl Cl+ Cl Cl Cl Cl
Single Bonds
Double Bonds
O O+ C + O OC O OC
Triple Bonds
N N+ N N
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Resonance Forms
OO
O OO
O
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•Molecules with an odd number of electrons
•Molecules in which an atom has less than an octet
NO contains 5 + 6 = 11 electrons. No octet can be established
Though rare, these are most often encountered in compoundsof Born and Beryllium
B
FF
F
Exceptions to the Octet Rules
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Molecules in which an atom has more than an octetThis is observed in compounds constructed from period 3 elements and beyond
PCl
Cl
Cl
Cl
Cl
3s 3p 3d
Exceptions to the Octet Rules
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Strengths of Covalent Bonds
Bond dissociation Energy (Bond Energy): is the enthalpy change (H) required to break a particular bond in a mole of gaseous substance
(g) Cl Cl Cl2 (g) H = 242 kJ
Bond Energies and the Enthalpy of Reactions
H = (bond energies of bonds broken) - (bond energies of bonds formed)
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H = (bond energies of bonds broken) - (bond energies of bonds formed)Cl2(g) + H-CH3 H-Cl(g) + CH3Cl
H = [(Cl-Cl) + 4(H-C)] - [(Cl-Cl) + 3(H-C) + (Cl-C)] H = [242 kJ+4(413 kJ)]-[431 kJ + 4(413kJ) + (328)] = -104 kJ
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Bond Strength and Bond Length
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Electronegativity and Bond Polarity
“the ability of an atom in a molecule to attract electrons to itself”
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Electronegativity and Bond Polarity
H2 : Ediff = 2.1 -2.1 = 0
HCl: Ediff = 3.0 -2.1 = 0.9
Cl2 : Ediff = 3.0 - 3.0 = 0
note that LiF is ionic : Ediff = 4.0 - 1.0 = 3.0
H Cl
H Cl+ -
BH3 2.1-2.0 = .1
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Ionic Character The bigger the electronegativity difference
the more ionic character. 1.4 has more ionic character than 1.2
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noble gas configurations
Cl1-
Na1+
Cu1+
Sn2+
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Isoelectronic O2-, Cl1-, Ne, Na1+, Mg2+
size trend
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energy diagram page 366