Polarizing power of cation Polarizability of Anion B The ability to distort the electron a The ease of the electron cloud being distorted distribution of adjacent ions or atom. by the influence of adjacent ion or atom. bThe polarizing power of cation is favored by w The more polarizable anion would Id have higher charge and smaller size to have a higher charge and larger size higher charge density PAF+>Mg2+>Na+ Lit> Nat Polarization Effect on AB, Structures(A= Transition Metal Polarization aSame r/, larger size of anion induced more increasing Polarization part of electrons are active in the whole crystal, property of semiconductor and in bonding Hela layer , pe metal, such as Fes, smaller cation has more polarizing lavers/chains crystals to molecule crystals along vertical axi Sisa chain Covalent Crystals一 Covalent Bonding Held Together by Covalent Bond Review some important features of covalent Share electrons lead to strongest bond a Some Properties Basic Concepts of Molecular Orbital Theory Very hard half· filled orbital High melting points hybrid orbital Insulators/semiconductors Atomic orbital molecular orbital bonding(symmetric) molecular orbital tric) molecular orbital9 Polarizing Power of Cation The ability to distort the electron distribution of adjacent ions or atom. The polarizing power of cation is favored by higher charge and smaller size Þ to have a higher charge density Al3+ > Mg2+ > Na+ Li+ > Na+ Polarizability of Anion The ease of the electron cloud being distorted by the influence of adjacent ion or atom. The more polarizable anion would have higher charge and larger size S2- > O2- S2- > Cl￾Polarization Effect on AB2 Structures (A = Transition Metal) Same r+ /r- , larger size of anion induced more polarizable anion ® part of electrons are active in the whole crystal ® property of semiconductor and metal, such as FeS2 smaller cation has more polarizing power ® ion crystals to molecule crystals along vertical axis. Polarization Increasing Polarization in bonding low-dimensionality ¾¾ layers/chains Covalent Crystals ¾ Held Together by Covalent Bonds Share electrons lead to strongest bonds Some Properties: - Very hard. - High melting points. - Insulators/semiconductors. Covalent Bonding Review some important features of covalent bonding: ßBasic Concepts of Molecular Orbital Theory half-filled orbital hybrid orbital atomic orbital & molecular orbital bonding (symmetric) molecular orbital antibonding (antisymmetric) molecular orbital