Chemical bonding
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Chemical bonding

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    Chemical bonding Chemical bonding Document Transcript

    • High School Chemistry Rapid Learning Series - 15 Rapid Learning Center Chemistry :: Biology :: Physics :: Math Rapid Learning Center Presents … p g Teach Yourself High School Chemistry in 24 Hours 1/32 http://www.RapidLearningCenter.com Chemical Bonding HS Ch i t R id Learning Series Chemistry Rapid L i S i Wayne Huang, PhD Kelly Deters, PhD Russell Dahl, PhD Elizabeth James, PhD Rapid Learning Center www.RapidLearningCenter.com/ © Rapid Learning Inc. All rights reserved. © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 1
    • High School Chemistry Rapid Learning Series - 15 Learning Objectives By completing this tutorial you will learn… 4 types of bonds and the properties associated with those bond types. Bond Polarity. Valence Bond Theory. 3/32 Concept Map Previous content Chemistry New content Ionic Nonpolar Covalent C l t Polar Covalent Studies Matter 4 types of bonding One type is Metallic Compounds Valance Bond Theory Most simple bonding theory 4/32 © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 2
    • High School Chemistry Rapid Learning Series - 15 Types of Chemical Bonds 5/32 Definition: Ionic Bond Ionic Bond – Formed from the electrostatic attraction between positive and negatively charged ions due to transfer of electrons contains both metals and non-metals. Na+ Cl- A sodium atom loses an electron to form Na+ and a chlorine atom gains that electron to form Cl-. An ionic bond is formed between them. 6/32 © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 3
    • High School Chemistry Rapid Learning Series - 15 Definition: Covalent Bond Covalent Bond – Two nonmetals share electrons to form a bond (e.g. CH4) (e g ). H Sharing 4 pairs of electrons between 4xH and 1xC atoms H C H H 7/32 Definition: Polar Covalent Bond Polar Covalent Bond – Two non-metals share electrons unevenly electrons are closer to one atom than the other. H C N 8/32 © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 4
    • High School Chemistry Rapid Learning Series - 15 Definition: Metallic Bond Metallic Bond – Metal atoms join together and j g pool their electrons in a large network. Cu Cu Cu C Cu Cu 9/32 Four Types of Bonds The different bond types have different properties. Happens between Electrons are Characteristics Metals & Nonmetals Transferred from one atom to another to create ions. High melting points, brittle, often dissolve in water, conduct electricity when aqueous. Non-metals Shared between 2 atoms. Low melting points, do not often dissolve in water, do not conduct electricity when aqueous. Polar Covalent Non-Metals Shared unevenly between 2 atoms. Medium melting points, sometimes dissolve in water, do not conduct electricity when aqueous. Metallic Metals Shared in a large pool with all the atoms. Soft, conductors of heat and electricity, do not dissolve in water. Ionic Covalent 10/32 © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 5
    • High School Chemistry Rapid Learning Series - 15 Bond Polarity 11/32 Definition: Polar Bond Polar Bond – uneven sharing of electrons due to differences in electronegativity (i.e. CO2). The “pull” an atom has for electrons it’s sharing in a bond. Oxygen is more electronegative than Carbon. The Oxygen will pull on the electrons harder. The electrons will move closer to the Oxygen Oxygen. δ+ δ- O C δ- O 12/32 © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com This will leave the Carbon with a partial positive charge and Oxygen with a partial negative charge. Note: Due to its symmetry, CO2 molecule is nonpolar. Its linear structure does not have any overall polarity because the two polar bonds cancel each other out. 6
    • High School Chemistry Rapid Learning Series - 15 Electronegativity Trends In general, electronegativity: Increases Decreases 13/32 Common Element Electronegativities Here are 8 common elements & their electronegativities. Element H 2.1 C 2.5 N 3.0 O 3.5 F 4.0 S 2.5 Cl 3.0 Br 14/32 Electronegativity 2.8 Electronegativity Mnemonic: F > O > N > Cl > Br > S > C > H = FON (fun) Clown Brings Such CHaos. © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 7
    • High School Chemistry Rapid Learning Series - 15 Determining a Polar Bond 1 Look up the electronegativities for the two atoms. 2 Determine the (absolute value) difference in electronegativity. electronegativity Differences of: 0 0.4 = Non-polar covalent bond 0.5 1.4 = polar covalent bond > 1.4 = ionic bond 3 If there is a polar bond, indicate it with an arrow being drawn toward the more electronegative element with a cross on the tail. Example: C–H 15/32 Determine if each is a polar bond. C = 2.5 H = 2.1 Difference = 0.4 Non-polar C–N C = 2.5 N = 3.0 Difference = 0.5 Polar Definition: Polar Molecules Polar Molecule – Polar bonds do not cancel out and the molecule overall has partially positive and partially negative areas. areas δ- O C O O H H δ+ Polar bonds, but non-polar molecule Polar bonds, polar molecule 16/32 © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 8
    • High School Chemistry Rapid Learning Series - 15 Polar Molecules and Bond Geometry The manner in which we draw a molecule could affect our determination of polarity. δ δ- O H O H H H δ+ Drawing water in this way makes it appear to be a non-polar molecule. Wrong! However, water actually is shaped like this, and it is a polar molecule. It is important to know the actual 3D arrangement to determine polarity of a molecule. 17/32 Determining Bond Types 18/32 © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 9
    • High School Chemistry Rapid Learning Series - 15 Bond Type Flow Chart Compound contains Metal & Non-metal Ionic Bonding (MgCl2) Non-metals only Electronegativity Electronegativity difference difference 0 - 0.4 0.5 – 1.4 Covalent Bonding (Cl2) Metals only Metallic Bonding (Mg metal) Polar Covalent Bonding (HCl) 19/32 Determining Bond Type Example Example: Determine the bond type of each: K–O Metal & non metal non-metal Ionic Bonding C–O Non-metals C = 2.5 O = 3.5 Difference = 1.0 Polar Covalent C–S Non-metals C = 2.5 S = 2.5 Difference = 0 Covalent 20/32 © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 10
    • High School Chemistry Rapid Learning Series - 15 Valence Bond Theory 21/32 Definition: Valence Bond Theory Valence Bond Theory – Bonds are formed by the orbitals of atoms overlapping overlapping. Valence Bond H H H H s-orbital 22/32 Valence Bond – A chemical bond formed by sharing valence electrons. A valence electron, for a main group element, is in the outermost electron shell. For a transition metal, it can also be in an inner shell. © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 11
    • High School Chemistry Rapid Learning Series - 15 Sigma & Pi Bonds 23/32 Definition: Sigma Bond - 1 Sigma Bond (σ bond) – A bond in which one pair of electrons is shared. It is formed from the overlap of 2 s-orbitals as below (head to s orbitals (head-tohead overlap). H H s-orbital 2 hydrogen atoms - each has 1 electron in an s-orbital. 24/32 © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 12
    • High School Chemistry Rapid Learning Series - 15 Definition: Sigma Bond - 2 Sigma Bond (σ bond) – A bond in which one pair of electrons is shared. It is formed from the overlap of 2 s orbitals as below (head to s-orbitals (head-tohead overlap). sigma bond H H H H 2 hydrogen atoms - each have 1 electron in an s-orbital. 25/32 As the atoms move together, their s-orbitals overlap and form a sigma bond. Definition: Pi Bond - 1 Pi Bond (π bond) – 2nd or 3rd bond between two atoms. It is formed from parallel p-orbitals (side-to-side overlap). p-orbital O O s-orbital 26/32 Only the orbitals and electrons involved in this bond will be shown. © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 13
    • High School Chemistry Rapid Learning Series - 15 Definition: Pi Bond - 2 Pi Bond (π bond) – 2nd or 3rd bond between two atoms. Formed from parallel p-orbitals (side-to-side overlap). pi bond O O O O sigma bond 27/32 Counting Bonds How many sigma and pi bonds are in a molecule? σ Each first bond between 2 atoms is a sigma bond. π All 2nd and 3rd bonds between 2 atoms are pi bonds. Example: Count the sigma and pi bonds in the following molecule: H H H C C C N σ 6 5 4 3 2 1 π 3 2 1 28/32 © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 14
    • High School Chemistry Rapid Learning Series - 15 Diatomic and Polyatomic Compounds The Valence Bond Theory works well for diatomic compounds (H2, O2, etc.). But what about polyatomic compounds, such as CH4? More complex theories, such as Hybridization and Molecular Orbital Theory are introduced in more advanced chemistry courses. 29/32 Learning Summary The type of bond can be determined from the atoms involved, and each type has common properties. The Valence Bond Theory uses the overlap of atomic orbitals for diatomic compounds. The first bond between two atoms is a σ bond, each addition bond is a π bond. 30/32 © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 15
    • High School Chemistry Rapid Learning Series - 15 Congratulations You have successfully completed the tutorial Chemical Bonding Rapid Learning Center Rapid Learning Center Chemistry :: Biology :: Physics :: Math What’s N t Wh t’ Next … Step 1: Concepts – Core Tutorial (Just Completed) Step 2: Practice – Interactive Problem Drill Step 3: Recap – Super Review Cheat Sheet Go for it! 32/32 http://www.RapidLearningCenter.com © Rapid Learning Inc. All rights reserved. :: http://www.RapidLearningCenter.com 16