CHEM102 1st Edition Lecture 4Outline of Last LectureI. Molecular Massa. Definitions and how to find itII. The Molea. Definitions and how to calculate moles to grams and grams to molesIII. Molar Massa. Definition and hot to find itIV. Lewis electron-dot structuresa. Definition and how to draw them Outline of Current Lecture I. Molecular Structure and Bondinga. Definitions and hoe to determine themCurrent LectureMolecular Structure and BondingVSEPR = Valence Shell Electron-Pair Repulsion ModelElectron Pair Geometry: the electron pair geometry for a molecule can be linear, trigonal planar, or tetrahedral, depending on what the steric number is (See definition of Steric number).(See picture for example)Molecular Geometry: The molecular geometry of a molecule can be linear, trigonal planar, tetrahedral, trigonal pyramidal, or bent, depending on how many lone electron pairs there are (See picture for example)Steric Number: number of areas with electrons around the central atom (See Picture)*Remember to always label a molecule in terms of the central atom*These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Electrons will want to get as far away from each other as possible when is come to molecular structure, so they create bond anglesBond Angles: the angle between each electron of a molecule (See picture for example)Ex. What is the electron pair geometry for CH4?1. Write the Lewis Structure for CH42. Find the Steric Number (number of areas with electrons around the central atom)3. Determine if it is Linear, Trigonal Planar, or Tetrahedral- To determine whether it is Linear, Trigonal Planar, or tetrahedral, look at the stericnumber. If it is 2, the molecule is linear. If it is 3, the molecule is Trigonal Planar. If it is 4, the molecule is Tetrahedral.4. Draw the molecule(See pictures for this example)*To determine the Molecular geometry, you must first find the Electron Pair Geometry*Ex. What is the molecular geometry of CH41. If the atom has no lone pairs of electrons, the Electron pair geometry will be same as theMolecular Geometry. Like in CH4, there are no lone pairs of electrons therefore the Electron Pair geometry and Molecular geometry are both Tetrahedral. 2. If there are lone pairs of electrons, cover them up with your finger and see what shape you have ( either linear, trigonal planar, tetrahedral, trigonal pyramidal or bent) ( See picture) Ex. What is the Electron Pair Geometry and Molecular Geometry of NH3? (Do this on our own)Intermolecular attractions*only polar molecules have dipole-dipole attraction** to find out whether a molecule is polar or not, look at the atoms surrounding the central atom. If everything is the same, it is non-polar. If something’s are different, it is polar. (See pictures)* Dipole-dipole attraction: results from the electrostatic forces between molecular dipoles. So, opposites attract in this type. Each molecule in dipole-dipole attraction has 2 poles, one is positive one is negative. Molecules with the opposite charges on each end are attracted to each other and form bonds.London Dispersion Forces: result from the attractions between instantaneous dipoles and induced dipoles. EVERYTHING has London Dispersion ForcesHydrogen Bonding: occurs between a hydrogen atom and a lone pair of electrons- Three rules for Hydrogen Bonding…1. The central atom must be either O, N, of F2. The molecule must of at least on pair of lone electrons on the central atom3. There must be a hydrogen atom bond to the central atom*In hydrogen bonds, the hydrogen atom is attracted to a pair of lone electrons and they form a bond.**hydrogen bonds can be shown with