repulsion of lone pairs are stronger

3.3 VSEPR theory you will:use the VSEPR theory of electron pairs to predict the spatial shape of molecules and ions Why is the water molecule bent? Why aren’t the 2 hydrogen atoms on a plane, exactly 180 degrees apart? Intro text kerek…When writing formulas of covalently bonded compounds, we do not show how they arranged in three-dimensional space. One way of showing molecular shape of compounds is to use valance shell electron repulsion model (VSEPR). It will be easier to start with molecules, which have only one central atom. In these types of molecules, lone pairs and shared electrons of the central atom repel each other, and tend to be in the state when they have minimum repulsion. Let’s take BeCl2 as an example. In this types of molecules two atoms of Cl tend to be in a state with minimum repulsion. It is achieved when two atom are located at 180o to each other. This shape is called a linear shape, and BeCl2 is a linear molecule.         Shape of BeCl2 molecule. In BF3 three fluorine atoms minimize the repulsion by locating themselves at 120o to each other. This arrangement is called a trigonal planar geometry.    Note that BeCl2 and BF3 do not follow the octet rule. The methane molecule (CH4) turns out to have a tetrahedral geometry, where each hydrogen atom is located at 109.5o to each other. 347363243You might expect linear geometry for H2O molecule as it has only two hydrogen atoms to oxygen atom. However, there are two additional lone pairs are also present in H2O molecule, which also repel each other and bonding electrons of H as well.  The repulsion of lone pairs are stronger than repulsions between bonding electrons. That is due to the fact that lone pairs take more volume (they are more diffused) compared to bonding electrons, thus, they repel each other more strongly than bonding electrons. The order or repulsion strength is: Lone pair – lone pair > lone pair – bonding electrons > bonding electrons – bonding electrons  347363243    Bend geometry of H2O moleculeThis arrangement is named a bend geometry. Due to the presence of lone pairs which repel bonding electrons more strongly, the angle between two hydrogen atoms is slightly less than tetrahedral geometry. The electron arrangement is  tetrahedral in shape, but the molecular shape is said to be bent. When we classify molecular shape we omit lone pairs. However, in electron arrangement of a molecule both lone pair and bonding electrons have to be taken into account. In addition the angle between two hydrogen atoms in water molecule is slightly less than 109.5o. The general procedure for finding the geometry of the molecule is given in the picture number. 347363252     Molecule geometries by VSEPR model1. Determine the molecular geometry of following compounds:CH2I2, ClF3, H2S, SO3, SO22. Use VSEPR theory to determine the shapes of each of the following. a. SCl2 b. PF3 c. NCl3 d. NH4+3. Use VSEPR theory to predict the geometry of the PCl3 molecule. 4. Using VSEPR theory predict the shape (molecular geometry) of COCl2 and is it polar or nonpolar. In 1985, Robert Curl and Harold Kroto received the Nobel Prize for the discovery of the fullerene C60. Fullerene is one of the allotrope of carbon that producing from graphite by using laser rays technology.  731420413 bend – ????????, ????????? / ????? bipyramidal – ????????????? / ???????????????

Go Top