Grade 10 Chemistry - Module 7 - Lesson 5 - Electronegativity and Polarity PDF

Grade 10: Chemistry Module 7:Covalent bonding Lesson 5: Electronegativity and Polarity WALT Explain the effect of electronegativity in covalent compounds polarity Teacher : Chemistry Team  Key Terms: Elect...

Grade 10: Chemistry Module 7:Covalent bonding Lesson 5: Electronegativity and Polarity WALT Explain the effect of electronegativity in covalent compounds polarity Teacher : Chemistry Team  Key Terms: Electronegativity – Polar Covalent Bond.  Essential Question: How is electronegativity used to determine the bond type? How do polar and nonpolar covalent bonds and polar and nonpolar molecules compare and contrast? What are the characteristics of covalently bonded compounds ?  Whoaaa How’s Your Mental Health Today You are loved  Starter: Group 1: Recall the explanation of the term electronegativity and mention the electronegativity on the periodic table Group 2: Relate between electronegativity, and ionic and covalent bonds Group 3: Critique how the electronegativity value of the atoms in a molecule can affect the location of electrons shared between them.  Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons. Noble gases are not listed because they generally do not form compounds. Electronegativity It is a measure of the tendency of an atom to attract electrons towards itself. It determines how the shared electrons are distributed between the two atoms in a bond. The more strongly an atom attracts the elections in its bonds, the larger its electronegativity. Approximate values.  What are the trends of electronegativity in the periodic table? Non-polar covalent bonds The electronegativity values derived by Pauling follow predictable periodic trends with the higher electronegativities toward the upper right of the periodic table. Page: 265  Electronegativity and Bond Character The value of the difference in the electronegativity of two bonded atoms, (ΔEN) provides a rough measure of the polarity to be expected in the bond and thus the bond type. As the electronegativity difference increases between two atoms, the bond becomes more ionic. What is the type of bond formed between two oxygen atoms? Fun Quote:  Tas Classify the bond type in the following bonds as ionic / Polar covalent and Non k Self Check polar a. H–H b. H–Cl c. Na–Cl Electron difference ΔEN : 0 0.9 2.2 Non-polar Covalent Polar Covalent Ionic bond. bond (Since the ΔEN ( Since the (Since ΔEN value is 0, value is between ΔEN value is the bonding electrons 0.4 and 1.7 ) greater than are shared equally 1.7) between the two atoms.)  Analyze the graph and answer the questions: Group 1: Compare the percentage of the ionic character in AlP and CaO Group 2: Explain why the polarity of AlP is considered weak compared to HF Group 3: Predict where would LiBr be plotted on the graph?  Tas Extra k Work Answer: non- polar covalent Answer: Ionic Answer: Polar Covalent  Extra Practice Symmetrical shapes: Asymmetric (non- Polar) shapes: (polar) Linear Bent / Angular Tetrahedral Trigonal pyramid. Trigonal planar  Two criteria to determine if a molecule is Polar or Non Polar: A Molecule will be Polar if : 1. The molecular shape around the central atom has a lone pair. (EXCEPT For Square Planar or Linear) 2. All atoms around the central atoms are not the same. Polarity and Molecular shapes: Note: If bonds are polar, asymmetrical molecules are polar and symmetrical molecules are nonpolar. Copyright © McGraw-Hill Education Electronegativity and Polarity Polar or non- polar covalent molecule: The given molecule is polar due to its asymmetry. 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. Notice that a tetrahedral molecule such as CCl4 is nonpolar. Another non polar molecule shown below is boron trifluoride, BF3. BF3 is a trigonal planar molecule and all three peripheral atoms are the same. Some examples of nonpolar molecules based on molecular geometry (BF3 and CCl4). The molecular geometry of a molecule affects its polarity. Each CO bond has a dipole moment, but they point in opposite directions so that the net CO2 molecule is nonpolar. In contrast, water is polar because the OH bond moments do not cancel out. To summarize, to be polar, a molecule must: 1.Contain at least one polar covalent bond. 2.Have a molecular structure such that the sum of the vectors of each bond dipole moment does not cancel.  Solution 1. Water is polar. Any molecule with lone pairs of electrons around the central atom is polar. 2. Methanol is polar. This is not a symmetric molecule. The −OH−OH side is different from the other 3 −H−H sides. 3. Hydrogen cyanide is polar. The molecule is not symmetric. The nitrogen and hydrogen have different electronegativities, creating an uneven pull on the electrons. 4. Oxygen is nonpolar. The molecule is symmetric. The two oxygen atoms pull on the electrons by exactly the same amount. 5. Propane is nonpolar, because it is symmetric, with HH atoms bonded to every side around the central atoms and no unshared pairs of electrons. Which of the following is a non-polar molecule: a. Boron trifluoride b. Nitrogen trifluoride.  Group 3 Group 2: Group 1 Draw the Lewis structure for the molecules SF4 and Identify each Determine whether a SF6 and PH2Br Analyze molecule as polar compound made of each structure to or non-polar : hydrogen and sulfur determine whether the SCl2 , CS2 and atoms is polar or molecule is polar or CF4. non-polar. nonpolar. Predict the type Determine the bond Predict the type of bond of bond that type present in water that will form between : will form molecule. H and S between Na and C and H S.  Assessment for learning : https://phet.co lorado.edu/en/ simulations/m olecule-polarit y Answer: Towards the more electronegative atom.  ab il i t lu b s o o l ar Starter! o f p y u l e l e c mo s i n e r ? w a t Let’s revisit polar vs non –polar molecules.  Page: 268 Solubility of Polar Molecules. Solubility is the property of a substance’s ability to dissolve in another substance. Polar molecules and ionic substances are usually soluble in polar substances. Non-polar molecules dissolve only in non-polar substances. “Like dissolves like” Will carbon tetrachloride dissolve in water?  In which solvent would Iodine (I2) most likely dissolve ?  Critical thinking No, detergents must be used because the polar water molecules cannot dissolve the nonpolar oil molecules.  Intermolecular forces: Covalent bonds between atoms are strong, but attraction forces between molecules are weak. The weak attraction forces are known as van der Waals forces. The forces vary in strength but are weaker than the bonds in a molecule or ions in an ionic compound. Non-polar molecules exhibit a weak dispersion force, or induced dipole. The force between two oppositely charged ends of two polar molecules is a dipole-dipole force. Example: A hydrogen bond is an especially strong dipole-dipole force between a hydrogen end of one dipole and a fluorine, oxygen, or nitrogen atom on another dipole. / dispersion forces/ London forces. Non – polar molecules do not have dipoles. So London dispersion force exists in non polar molecules.  Page: Properties of Covalent Compounds 270 & Covalent Network Solids. Many physical properties are due to intermolecular forces. Weak forces result in the relatively low melting and boiling points of molecular substances. paraffin Many covalent molecules are relatively soft solids. Molecules can align in a crystal lattice, similar to ionic solids but with less attraction between particles. Example,  Pg. 270 Solids composed of only atoms interconnected by a network of covalent bonds are called covalent network solids. Quartz and diamonds are two common examples of network solids. Extra info: Applications of Polarity:  Additional resources: Polar Covalent Bonds and Nonpolar Covalent bonds, Ionic Bonding - Types of Chemical Bonds https://www.youtube.com/watch?v=OvjkMqGzgiY How to Determine if Molecule is Polar or Nonpolar https://www.youtube.com/watch?v=v1Kp3yEIW C0 What are intermolecular forces? https://www.youtube.com/watch?v=XbDeEdr7OQI Polarity explanations + Online Practice. https://www.liveworksheets.com/oi280375zr  Group 3 Group 1 The refrigerant known as 1. Predict which freon-14 is an Group 2: bond is the most ozone-damaging polar. compound with the Determine if these formula CF4. Why molecules and is the CF4 molecule ions are polar. 2. Use Lewis nonpolar even though it Explain your contains structures to predict answers. polar bonds? A. H3O+ b. PCl5 the molecular c. H2S polarities of SO2 - SF4 – SF6.