More Related Content
Similar to #4 Shapes and Properties- Polar and Nonpolar Molecules.pptx (20)
![CHEMICAL BONDING AND MOLECULAR STRUCTURE [PART: 3], CLASS 11 CHEMISTRY](https://cdn.slidesharecdn.com/ss_thumbnails/cb4-250226043559-bf93a4b4-thumbnail.jpg?width=560&fit=bounds)
#4 Shapes and Properties- Polar and Nonpolar Molecules.pptx
- 1. SHAPES AND PROPERTIES- POLAR AND NONPOLAR MOLECULES Jessa Mae E. Gastar
- 2. Polar and Nonpolar Molecules (Shapes and Properties) MELC Determine if a molecule is polar or non-polar given its structure Code S11/12PS-IIIc-15
- 3. Molecular Polarity ◦ To determine if a molecule is polar or nonpolar, it is frequently useful to look at Lewis structures. ◦ Nonpolar compounds will be symmetric, meaning all of the sides around the central atom are identical - bonded to the same element with no unshared pairs of electrons.
- 4. ◦ Polar molecules are asymmetric, either containing lone pairs of electrons on a central atom or having atoms with different electronegativities bonded. ◦ A polar molecule is a molecule in which one end of the molecule is slightly positive, while the other end is slightly negative. Molecular Polarity
- 5. SUMMARY Polar molecules Non-polar molecules The molecules having positively charged end and negatively charged end due to the difference in the charges of atoms present in the molecules are polar molecules. The molecules that do not have such separation of electric charges are nonpolar. Most of the polar molecules have an asymmetric or uneven distribution of electrons. Nonpolar molecules have a symmetrical distribution of electrons. When highly electronegative atom bonds with a relatively less electronegative atom, polar molecules are formed. Nonpolar molecules are formed when there is quite a little difference in the electronegativities of the atoms forming bonds in the molecule. Due to the separation of electric charges, there is a net dipole moment in the polar molecules. As there is no separation of electric charges, there is no net dipole moment in nonpolar molecules. These molecules react with polar molecules to form solutions. Nonpolar molecules do not have such reactivity. Polar molecules dissolve in polar molecules only. Nonpolar molecules also dissolve in nonpolar molecules only. Water is a polar molecule as there is a difference in electronegativities of Oxygen and Hydrogen atoms. All hydrocarbons are mostly nonpolar.
- 6. Valence-Shell Electron-Pair Repulsion Theory (VSEPR) ◦ There is no direct relationship between the formula of a compound and the shape of its molecules. The shapes of these molecules can be predicted from their Lewis structures, however, with a model developed about 30 years ago, known as the valence-shell electron-pair repulsion (VSEPR) theory. ◦ The VSEPR theory assumes that each atom in a molecule will achieve a geometry that minimizes the repulsion between electrons in the valence shell of that atom.
- 8. Predicting the Shapes of Molecules: The following steps must be followed in order to decide the shape of a molecule. ◦ The least electronegative atom must be selected as the central atom (since this atom has the highest ability to share its electrons with the other atoms belonging to the molecule). ◦ The total number of electrons belonging to the outermost shell of the central atom must be counted. ◦ The total number of electrons belonging to other atoms and used in bonds with the central atom must be counted. ◦ These two values must be added in order to obtain the valence shell electron pair number or the VSEP number.
- 9. ◦ Electronegativity is defined as an atom’s ability to attract electrons towards it in a chemical bond.
- 10. LEWIS ELECTRON DOT STRUCTURE ◦ A Lewis Structure is a very simplified representation of the valence shell electrons in a molecule. ◦ It is used to show how the electrons are arranged around individual atoms in a molecule. ◦ Electrons are shown as "dots" or for bonding electrons as a line between the two atoms. The goal is to obtain the "best" electron configuration, i.e. the octet rule and formal charges need to be satisfied.
- 12. ◦ Remember: ◦ The number of valence electrons for an element is usually the same as its group number of on the periodic table (except for helium and the metals). ◦ If the molecule has a charge, subtract one electron for each positive charge or add one electron for each negative charge. For example, for NO3 –, you have 5 electrons for the nitrogen atom and 3 x 6 = 18 electrons for the oxygen atoms, plus one valence electron for the net charge, giving a total of 24 valence electrons (5 + 18 + 1).
- 13. Example:
- 14. Let’s try! ◦ Write Lewis structures for the following: (please note, none of the solutions are using the expanded octet rule or formal charges) 1. HBr 2. PCl3 3. SF2 4. H2CCH2 5. HNNH 6. H2CNH 7. NO– 8. N2 9. CO 10. CN–
- 16. ◦ https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physi cal_and_Theoretical_Chemistry)/Physical_Properties_of_Matter/Atomic_and_Molecular_Properties/Lewis_Structures#:~:text= A%20Lewis%20Structure%20is%20a,line%20between%20the%20two%20atoms. ◦ https://chemed.chem.purdue.edu/genchem/topicreview/bp/ch8/vsepr.html ◦ https://byjus.com/jee/vsepr-theory/ ◦ https://chemistrytalk.org/electronegativity-chart-trends/ ◦ https://geometryofmolecules.com/how-to-determine-molecule-polar-non-polar/ ◦ https://sciencenotes.org/how-to-draw-a-lewis-structure/