Lecture 12 Date: 10/17/2024 Content: Electronegativity: The ability of an atom to attract electron density to itself (from or to another atom type). Consider each atom's ease to ionize (remove e-) and EA (give and take). Going across, EN increases; going down, EN decreases. Shows likeliness to pull another atom to itself. Most EN (wants e- density) is F. Low E orbitals of valence e-: better place to put e-s. Heteronuclear/Diatomics If EN(A) = EN(B): Symmetrical 2s almost becomes 2σ 2p almost becomes 2π If EN(A) < EN(B): Asymmetrical Smaller diff. in E → MO not too different from AO B (bigger share of e-s) from bonding orbitals. Not only is good physical overlap is needed but good E overlap. With a very large E separation, interaction → remain AOs With unequal E, more E goes into bonding orb. and less to antibonding orb. Higher EN is associated with: a) 1e- valence orbitals b) 1e- valence orbitals c) 2e- valence orbitals d) 4e- valence orbitals Covalent (model): (2s-2s, 2p-2p, etc.) CO (small diff in EN): Number of e- from C is 4, from O is 6 - 10 e- Isoelectronic: Same number of electrons. CO is isoelectronic to N₂. O more EN than C Diagrams: Several diagrams depicting molecular orbitals (MOs) are shown, likely illustrating the formation of MOs in CO and comparing them to N₂. The diagrams show atomic orbitals (AOs) combining to form bonding and antibonding MOs. Labels like "σ", "π", "2s", "2p", "bonding", "antibonding" are used to indicate the types of orbitals and their interactions. Key Points: C and O can mix 2s and 2p orbitals. O has more bonding probability. C has more antibonding probability. 2s does not have to mix with 2s; may be whatever valence orbitals are. Ex. with S and O HCl (large diff in EN-ionic): S of H line up with is of Cl (much greater E (nuclear charge, EN) H 1s Cl 1s 2s 2p 3s 1s 1s 2s 2p 3s 3p 1s 2s 2p 3s 3p σ 1s σ 1s σ 2s σ 2s σ 2p σ* 2p π 2p π* 2p** 2s 2p 3s 3p 3p no interaction HCI H Cl more like 1s more like 3p goes in no orbitals, 2 in σ MD resembles AD of Cl as if H gives e-s to Cl, but there's stabilization from σ 2p as E ↑ than nos alone