UNIT 1: Structure and Properties of Matter Atomic Models and Properties of Atoms Chemical Bonding and Properties of Matter UNIT Chapter 4: Chemical Bonding and Properties of Matter Chapter 4: Chemical Bonding and Properties of Matter The chemical bonding in a substance influences the shape of its molecules, and molecular shape influences the properties of that substance One of the properties of iron is its strength, which makes it ideal for use in support structures The strength of iron makes it useful in items such as horseshoes TO PREVIOUS SLIDE UNIT Chapter 4: Chemical Bonding and Properties of Matter 4.1 Models of Chemical Bonding Three types of chemical bonding are ionic, covalent, and metallic TO PREVIOUS SLIDE Section 4.1 UNIT Chapter 4: Chemical Bonding and Properties of Matter Section 4.1 Electronegativity Electronegativity is the relative ability of an atom to attract shared electrons in a chemical bond TO PREVIOUS SLIDE What general trends in electronegativity are shown in the periodic table? UNIT Chapter 4: Chemical Bonding and Properties of Section 4.1 Matter Electron Sharing and Electronegativity Electronegativity difference, ΔEN, between two atoms bonded together can be low, intermediate, or high The electron density diagrams below show the differences in the bonds • when ΔEN is 0: electrons are equally shared • when ΔEN is 1: electrons are more closely associated with the more electronegative atom • when ΔEN is high, there is little sharing of electrons TO PREVIOUS SLIDE Bonding is a continuum between equal sharing and minimal sharing of electrons UNIT Chapter 4: Chemical Bonding and Properties of Section 4.1 Matter Electron Sharing and Electronegativity Scientists have categorized types of bonds according to ΔEN • ΔEN between 1.7 and 3.3: mostly ionic • ΔEN between 0.4 and 1.7: polar covalent • ΔEN between 0.0 and 0.4: mostly covalent (non-polar) TO PREVIOUS SLIDE Three categories of bonds have been set based on ΔEN UNIT Chapter 4: Chemical Bonding and Properties of Section 4.1 Matter Metallic Bonding Chemists use the electron-sea model to describe metallic bonding The model proposes that the valence electrons of metal atoms move freely among the ions, forming a “sea” of delocalized electrons that hold the metal ions rigidly in place Microscopic analysis shows that the structure of metals consists of aggregates of crystals TO PREVIOUS SLIDE UNIT Chapter 4: Chemical Bonding and Properties of Section 4.1 Matter Properties of Metals Melting and Boiling Points • the stronger the bonding forces, the higher the melting and boiling points of pure metals Periodic table trends include: For Group 1, melting points decrease as the atomic number increases TO PREVIOUS SLIDE For Groups to 6, across a period, melting points increase as atomic number increases UNIT Chapter 4: Chemical Bonding and Properties of Matter Properties of Metals Electrical and Thermal Conductivity • Metals are good conductors because their electrons are free to move from one atom to the next Malleability and Ductility • Based on the electron-sea model, metals can be shaped because, when struck, the metal ions can slide by one another while the electrons still surround them Hardness • The variation between metals is due to differences in crystal size (smaller ones make harder metals) TO PREVIOUS SLIDE Section 4.1 UNIT Chapter 4: Chemical Bonding and Properties of Matter Section 4.1 Alloys Alloys are solid mixtures of two or more metals • the addition of the second metal, even in a very small amount, can significantly affect the properties of a substance • in some cases, non-metal atoms, such as carbon, are added TO PREVIOUS SLIDE If atoms of the second metal are similar in size to the first metal, they take the place of those atoms If atoms of the second metal are much smaller than atoms of the first metal, they will fit in spaces between the larger atoms UNIT Chapter 4: Chemical Bonding and Properties of Section 4.2 Matter Guidelines for Using VSEPR Theory to Predict Molecular Shape TO PREVIOUS SLIDE UNIT Chapter 3: Atomic Models and Properties of Atoms Section 3.2 Learning Check What is the electron-group arrangement and molecular shape of HCN? TO PREVIOUS SLIDE Answer on the next slide UNIT Chapter 3: Atomic Models and Properties of Atoms Learning Check HCN has two bonding groups and no lone pairs The electron-group arrangement is linear, and the shape of the molecule is also linear TO PREVIOUS SLIDE Section 3.2 UNIT Chapter 4: Chemical Bonding and Properties of Section 4.2 Matter The Influence of Molecular Shape on Polarity The shape of a molecule affects that molecule’s polarity • polar bonds have a bond dipole • bond dipoles are indicated using vectors that point in the direction of higher electron density In a polar covalent bond, a partial positive charge is associated with one atom and a partial negative charge is associated with the other atom TO PREVIOUS SLIDE UNIT Chapter 4: Chemical Bonding and Properties of Section 4.2 Matter Determining Whether a Molecule is Polar A molecule with one or more polar bonds is not necessarily a polar molecule The molecule’s shape must be considered The polarity as a whole can be determined by adding the vectors TO PREVIOUS SLIDE Both water and carbon dioxide have two polar bonds But water’s bent shape results in a polar molecule, while carbon dioxide’s linear shape results in a non-polar molecule UNIT Chapter 4: Chemical Bonding and Properties of Matter Molecular Shapes and Polarities TO PREVIOUS SLIDE Section 4.2 UNIT Chapter 4: Chemical Bonding and Properties of Section 4.2 Matter How Intermolecular Forces Affect the Properties of Solids and Liquids Intermolecular forces exist between ions and molecules and influence the physical properties of substances Categories of forces: • dipole-dipole • ion-dipole TO PREVIOUS SLIDE • induced dipole • dispersion UNIT Chapter 4: Chemical Bonding and Properties of Matter Section 4.2 Dipole-Dipole Dipole-dipole forces: • are forces of attraction between polar molecules, which have a region of partial positive charge and a region of partial negative charge • are a main reason for melting and boiling point differences between polar and non-polar molecules • include hydrogen bonding, as an example of one type Hydrogen bonding (dotted lines) in water TO PREVIOUS SLIDE UNIT Chapter 4: Chemical Bonding and Properties of Section 4.2 Matter Ion-Dipole Ion-dipole forces: • are forces of attraction between partial charges on polar molecules and ions • depend on the size and charge of the ion and the magnitude of the partial charge and size of the molecule • are involved in the process of hydration Ion-dipole intermolecular forces TO PREVIOUS SLIDE UNIT Chapter 4: Chemical Bonding and Properties of Matter Section 4.2 Induced Dipoles Dipole-induced dipole forces: are forces of attraction between a polar molecule and a non-polar molecule that has an induced (temporary) dipole due to the nearby polar molecule Ion-induced dipole forces: are forces of attraction between an ion and a non-polar molecule that has an induced dipole due to the nearby ion A dipole can be induced in a non-polar molecule TO PREVIOUS SLIDE UNIT Chapter 4: Chemical Bonding and Properties of Matter Section 4.2 Dispersion Forces Dispersion forces: are forces of attraction between all molecules, including non-polar molecules are due to spontaneous temporary dipoles that form due to the constant motion of electrons in covalent bonds depend on the size and shape of the molecules • the larger and more linear the molecule, the greater the force of attraction TO PREVIOUS SLIDE The more linear molecule has a higher boiling point because the dispersion forces are greater UNIT Chapter 4: Chemical Bonding and Properties of Matter TO PREVIOUS SLIDE Section 4.2 Review Section 4.2 Hydrogen Bonding A hydrogen bond is the attractive interaction of a hydrogen atom and an electronegative atom, such as nitrogen, oxygen or fluorine, that comes from another molecule or chemical group It is not a true chemical bond The hydrogen has a polar bonding to another electronegative atom to create the bond These bonds can occur between molecules (intermolecularly), or within different parts of a single molecule (intramolecularly) Examples of intermolecular H- bonding: Water, HF Examples of intramolecular H – Bonding: HF, HCl HBr, HI – boiling points HF > HI > HBr > HCl HF has highest boiling point because of intermolecular hydrogen bonding HI has the higher boiling point compared to HCl because of dipole-dipole interactions due to large size of Iodide molecule Due to larger size of iodide, induced polarity is greater and hence stronger the bond formed, and thus higher the boiling point [...]... 4: Chemical Bonding and Properties of Matter TO PREVIOUS SLIDE Section 4 .1 Review Section 4 .1 UNIT 2 Chapter 4: Chemical Bonding and Properties of Section 4.2 Matter 4.2 Shapes, Intermolecular Forces, and Properties of Molecules Molecular compounds form a much greater variety of structures than ionic compounds form Understanding the properties of molecules requires an understanding of their three-dimensional... TO PREVIOUS SLIDE UNIT 2 Chapter 4: Chemical Bonding and Properties of Section 4 .1 Matter Learning Check Describe the chemical bonding and structure of NaCl How do bonding and structure influence the general properties of the substance? TO PREVIOUS SLIDE Answer on the next slide UNIT 2 Chapter 4: Chemical Bonding and Properties of Section 4 .1 Matter Learning Check NaCl is composed of a metal atom bonded.. .UNIT 2 Chapter 4: Chemical Bonding and Properties of Matter Ionic Bonding • occurs when ΔEN is between 1. 7 and 3.3 • essentially, involves one atom losing one or more electrons and another atom gaining those electron(s) There are different ways to show the transfer of electrons in the formation of ionic compounds TO PREVIOUS SLIDE Section 4 .1 UNIT 2 Chapter 4: Chemical Bonding and Properties of Matter. .. PREVIOUS SLIDE UNIT 2 Chapter 4: Chemical Bonding and Properties of Section 4 .1 Matter Explaining Triple Bonds For molecules like ethyne: • the linear structure is explained by formation of 2 sp hybrid orbitals for each carbon (a 2s orbital + a 2p orbital) • sigma bonds form from overlap between sp of each carbon and between sp of carbons and 1s of hydrogens • two pi bonds form from overlap of the two... shapes Different theories and models are used to predict molecular shapes The shape of a molecule is the result of the presence of atoms, bonding electrons, and non-bonding electrons, as well as forces of attraction and repulsion TO PREVIOUS SLIDE UNIT 2 Chapter 4: Chemical Bonding and Properties of Section 4.2 Matter Depicting Two-Dimensional Structures of Molecules with Lewis Structures TO PREVIOUS... The four sp3 orbitals of C overlap with the s orbitals of H to form methane TO PREVIOUS SLIDE Section 4 .1 UNIT 2 Chapter 4: Chemical Bonding and Properties of Section 4 .1 Matter Explaining Double Bonds Hybrid orbitals are used to explain the structure of ethene or molecules like ethene TO PREVIOUS SLIDE • it is planar with ~12 0º bond angles • the structure is explained by formation of 3 sp2 hybrid orbitals... with two 2p orbitals) UNIT 2 Chapter 4: Chemical Bonding and Properties of Section 4 .1 Matter Explaining Double Bonds For bond formation in ethene: • one sp2 orbital of each carbon overlaps to form a σ bond between the carbons • two sp2 orbitals of each carbon overlap with the 1s orbitals of the hydrogens to form σ bonds • the lobes of the 2p orbitals of each carbon overlap above and below the plane... of Matter Section 4 .1 Ionic Crystals Ionic compounds exist as crystal lattice structures with particular patterns of alternating positive and negative ions The unit cell is the smallest group of ions that is repeated NaCl forms a cubic crystal lattice structure Different types of crystal structures can form • the relative sizes and charges of the ions affect the type of crystal structure that an ionic... overlap of the two 2p orbitals of each carbon TO PREVIOUS SLIDE UNIT 2 Chapter 4: Chemical Bonding and Properties of Section 4 .1 Matter Allotropes Allotropes are compounds that consist of the same element but have different physical properties An example is allotropes of carbon, which differ in the pattern of covalent bonds between carbon atoms TO PREVIOUS SLIDE Allotropes of carbon: A graphite, B diamond,... the greater the overlap, the stronger and more stable the bond • Atomic orbital hybridization is used to help explain the shapes of some molecules TO PREVIOUS SLIDE UNIT 2 Chapter 4: Chemical Bonding and Properties of Section 4 .1 Matter Quantum Mechanics and Bonding Molecular Orbital (MO) Theory explains bond formation and molecular shapes based on the formation of new molecular orbitals According to ... and Properties of Section 4.2 Matter Depicting Two-Dimensional Structures of Molecules with Lewis Structures TO PREVIOUS SLIDE UNIT Chapter 4: Chemical Bonding and Properties of Section 4.2 Matter. .. SLIDE UNIT Chapter 4: Chemical Bonding and Properties of Matter 4 .1 Models of Chemical Bonding Three types of chemical bonding are ionic, covalent, and metallic TO PREVIOUS SLIDE Section 4 .1 UNIT. .. structure of metals consists of aggregates of crystals TO PREVIOUS SLIDE UNIT Chapter 4: Chemical Bonding and Properties of Section 4 .1 Matter Properties of Metals Melting and Boiling Points • the