Molecular Shape And VSEPR
Molecular Shape andVSEPRUnit One
Lewis StructureuAtoms want to achieve Noble Gas configuration through bondsThe Octet Rule – atoms tend to have 8 electrons in thevalence shell which makes them stable and unreactiveThe larger the molecule/polyatomic ion becomes the more likely there maybe an exception to the “Octet Rule”
Lewis Structures for SimpleMolecules/Ions1.The least electronegative atom should be positioned as the “Central Atom”2.Hydrogen or Fluorine at positioned at ‘the end’ of a structure1.They will never be a central atom
Lewis Structures3.Determine total number of valence electrons3.4.Watch out for charges – especially on polyatomic ionsDetermine the total number of electrons needed for every atom toachieve noble gas electron configuration
Lewis Structure for More ComplexStructuresuCo-Ordinate Covalent BondsuCovalent – sharing of electron pairsWhen a filled atomic orbital overlaps with an emptyatomic orbitalEx. NH4
AmmoniumuNH4 - N is central atom, H is surroundinguValence ElectronsuuNoble Gas Electronsuuu1 N (5e-) 4H (1e-) – 1e- 8 electrons1 N (8e-) 4H (2e-) 16 electronsNumber of Shared / Bondsu16 electrons – 8 electrons 8u8 electrons / 2 electrons/bond 4 bondsNumber of non-bonding (unpaired) electronsu8 valence electrons – 8 shared electrons 0 lone pairs
AmmoniumPossible structure
Resonance StructuresSO2to satisfy the Octet RuleGive the same relative position of atoms, withdifferent places for bonding and lone pairs
Resonance StructuresuRequired by Molecules and IonsuNot “real” – but a weighted average between multiplestructures
Try These!uCO32-uNO uClO3-uSO32-
Expanded Valence LeveluAn exception to the octet ruleuAllows central atoms to maintain more than 8 electronsin the valence energyuArose from experiments and measurements of bondenergiesPhosphorus Pentachloride
Try These!uSF6uBrF5uXeF4uPF5
VSEPRuValence Shell Electron Pair Repulsion TheoryuRonald Gillespie and Ronald Nyholm (1957)Bonding and lone pairs in a valence levels of an atom repel oneanother. These electron pairs are “localized” in orbitals andwill try to be as far apart from one another as they can in orderto minimize energy
Indicating 3D Shapes
5 Basic Geometric ShapesBased off total number of electron groups
VSEPR Theory (Molecular Geometry)Specifies types of electron groups
VSEPR
VSEPR
Predicting Molecular ShapeuDraw a preliminary Lewis Structure based on formulauDetermine total number of electron groups around central atomuDouble/Triple bonds count as one electron groupuDetermine which geometric arrangement accommodates the total number ofelectron groupsuDetermine molecular shape
H3O Determine Molecular Shape of H3O uPossible Structure:uBonding/Lone Pairs: On oxygen – 3 bonding pairs, 1 lone pair4 groups totaluGeometrical Shape: Of the five basic shape – 4 groups isTetrahedraluMolecular Shape:With 3 BP and 1 LP the molecular shape isTrigonal Pyramidal
SiF62Determine Molecular Shape of SiF62Silicon has an expandedvalence shelluLewis Structure:uBonding/Lone Pairs: Central atom has 6 BP and 0 LP6 groups totaluGeometrical Shape: Of the five basic shapes 6 groups:OctahedraluMolecular Shape:For 6 BP the Molecular Shape is:Octahedral
Try These!Determine the geometric and molecular shape for thefollowing:BrCl4-CH2F2HCNAsCL5SO2NH4 SO3BF4-SO42-
Shape and PolarityShape and Polarity are directly related
DipoleuIn diatomic molecules bond polarity applies to the overall moleculeuPolyatomic molecules relies on all the bonds and angles and where they “cometogether”H
Shape and Polarity
Try These!Use VSEPR Theory to predict the shape of the following molecules.Determine whether the molecule is polar or not.CH3FCH2OGAI3
For 6 BP the Molecular Shape is: Octahedral. Try These! Determine the geometric and molecular shape for the following: BrCl 4-CH 2F 2 HCN AsCL 5 SO 2 NH 4 SO 3 BF 4-SO 4 2-Shape and Polarity Shape and Polarity are directly related . Dipole u In diatomic molecules bond polarity applies to the overall molecule
Jan 31, 2011 · the molecular geometries for each chemical species using VSEPR. Below the picture of each molecule write the name of the geometry (e. g. linear, trigonal planar, etc.). Although you do not need to name the molecular shape for molecules and ions with more than one "central atom", you should be able to indicate the molecular geometryFile Size: 890KBPage Count: 7Explore furtherLab # 13: Molecular Models Quiz- Answer Key - Mr Palermowww.mrpalermo.comAnswer key - CHEMISTRYsiprogram.weebly.comVirtual Molecular Model Kit - Vmols - CheMagicchemagic.orgMolecular Modeling 1 Chem Labchemlab.truman.eduHow to Use a Molecular Model for Learning . - Chemistry Hallchemistryhall.comRecommended to you b
This molecular shape corresponds to the VSEPR notation for this ion, AX3E . Practice Problem Use VSEPR theory to predict the molecular shape for each of the following: (a) HCN (b) SO 2
Lewis structures show the two-dimensional distribution of atoms and electrons. The molecular geometry, or three-dimensional shape of a molecule or polyatomic ion, can be determined using valence-shell electron-pair repulsion (abbreviated VSEPR and pronounced “VES-per”) theory, in
UNIT 4 – CHEMICAL BONDING AND MOLECULAR STRUCTURE Concept -VSEPR & VBT KNOWLEDGE One Mark Questions Q1. On the basis of VSEPR theory predict the shape of Hydronium (H 3O ) ion (L-1) Ans. p
AJR Ch10 Molecular Geometry.docx Slide 1 Chapter 10 Molecular Geometry (Ch9 Jespersen, Ch10 Chang) The arrangement of the atoms of a molecule in space is the molecular geometry. This is what gives the molecules their shape. Molecular shape is only discussed when there are three or more atoms connected (diatomic shape is obvious).
CHEM 1A: VSEPR Theory Now that we have an understanding of covalent bonding and how atoms share electrons to form molecules and polyatomic ions, we will use Lewis dot structures to predict electronic and molecular geometries.
Experiment Overview The purpose of this activity is to construct six models of VSEPR molecular geometrics from paper using origami folding techniques. Pre-Lab Questions (Use a separate sheet of paper to answer the questions.) 1. Write the Lewis electron-dot symbol for each of the following atoms: hydrogen, boron, nitrogen, silicon, sulfur, and bromine.
Python as his main programming language, primarily as a means for creative ends, because it is easy to read and fun to learn. J-P Stacey has been a senior developer at Torchbox Ltd since 2005, building and maintaining (among other things) Python, Django, and Drupal applications. He organizes the Oxford Geek Nights and gets involved in tuition and seminars at Torchbox. In his spare time he .
