General and Inorganic Chemistry I. - Lecture 1nlcd.elte.hu/szalai/pdf/lecture-5-handout.pdf · 5E...

General and Inorganic Chemistry I.Lecture 1

Istvan Szalai

Eotvos University

Istvan Szalai (Eotvos University) Lecture 1 1 / 29

Outline


Lewis Formulas and the Octet Rule

In most of their compounds, the representative elements (s and p field)achieve noble gas configurations.


Resonance and Delocalization


Dative Bond

[Fe(CN)]4−6


Limitations of the Octet Rule

Compounds in which the central element needs a share in less than eightvalence shell electrons. bigskip



Compounds in which the central element needs a share in more than eightvalence shell electrons.



Compounds or ions with odd number of electrons.


Bond Order

single bond (σ bond [s − s, s − p, p − p])

double bound (1 σ bond + 1 π bond [p − p])

triple bound (1 σ bond + 2 π bonds)


Bond Energy, Bond Length

bond length (pm) bond energy (kJ/mol)

H−H 74 436C−C 154 347N−N 140 159O−O 132 138F−F 128 159Si−Si 234 176

C=C 134 611O=O 121 498

C≡C 121 837N≡N 110 946


Bond Polarity, Dipole Moments

~µ = Q · ~d


Molecular Polarity

~µ = Q · ~d


Metallic Bond

It results from the electrical attractions among positively charged metalions and mobile, delocalized electrons belonging to the crystal as a whole.


Continuous Range of Bonding Types

∆EN = 0 apolar covalent or metallic bond0 < ∆EN < 2 polar covalent or metallic bond2 < ∆EN ionic bond


VSEPR Theory

Valence shell electron pair repulsion theory: Each set of valence shellelectrons on a central atom is significant. The sets of valence shellelectrons on the central atom repel one another. They are arranged aboutthe central atom so that repulsions among them are as small as possible.Lone pairs of electrons occupy more space than bonding pairs.

A: central atom, X: shared electron pairs, E: lone (unshared) pairs

AXnEm


VSEPR Theory

AX2 BeCl2, CdI2, HgBr2 linear

AX3 BF3,BF3, NO−3 trigonal planar

AX2E SO2, NO−2 angular


VSEPR Theory

AX4 CH4, CCl4, NH+4 tetrahedral

AX3E NH3, SO2−3 trigonal pyramidal

AX2E2 H2O angular


AX5 PF5, SbCl5 trigonal bipyramidal

AX4E SF4 seesaw

AX3E2 ClF3 T-shaped

AX2E3 XeF2, I−3 linear


AX6 SF6, SeF6 octahedral

AX5E BrF5 square pyramidal

AX4E2 XeF4 square planar


Valence Bond (VB) Theory

Valence bond theory describes covalent bonding as electron pair sharingthat results from the overlap of orbitals from two atoms. Usually, ”pureatomic” orbitals do not have the correct energies and orientations todescribe the where the electrons are when an atom is bounded to otheratoms. When other atoms are nearby as in a molecule, an atom cancombine its valence shell orbitals (hybridization) to form a new set oforbitals (hybrid orbitals).



Linear GeometryBeCl2: Be [He] 2s2 Cl [Ne] 3s2 3p5

Be 2s2 −−−−−→hybridize

sp



Trigonal Planar GeometryBF3: B [He] 2s2 2p1 F [He] 2s2 2p5

B 2s2 2p1 −−−−−→hybridize

sp2



Tetrahedral GeometryCH4: C [He] 2s2 2p2 H 1s1

C 2s2 2p2 −−−−−→hybridize

sp3



Trigonal Pyramidal GeometryH3: N [He] 2s2 2p3 H 1s1

N 2s2 2p3 −−−−−→hybridize

sp3



Angular GeometryH2O: O [He] 2s2 2p4 H 1s1

O 2s2 2p4 −−−−−→hybridize

sp3



Trigonal Bipyramidal GeometryPF5: P [Ne] 3s2 3p3 F [He] 2s2 2p5

P 3s2 3p3 −−−−−→hybridize

sp3d



Octahedral GeometrySF6: S [Ne] 3s2 3p4 F [He] 2s2 2p5

S 3s2 3p4 −−−−−→hybridize

sp3d2



Double BoundsA double consists of one sigma and one pi bond. A sigma bond resultingfrom head-on overlap of atomic orbitals. A pi bond resulting from side-onoverlap of atomic orbitals.C 2s2 2p2 −−−−−→

hybridizesp2



Triple BoundsA triple bound consists of one sigma and two pi bonds.C 2s2 2p2 −−−−−→

hybridizesp


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General and Inorganic Chemistry I. - Lecture 1nlcd.elte.hu/szalai/pdf/lecture-5-handout.pdf · 5E...

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