Bonding in Atoms What keeps us together

Valence Electrons Electrons located in the outer shell Readily available for bonding Always s or p sublevel Follows the Octet Rule Modeled by the Lewis Dot Diagram

The Octet Rule States that an atom will lose or gain electrons in order to fill the outer sublevels (s and p) Modeled by the Lewis Dot Diagram Gain of electrons = anion Loss of electrons = cations

Common Anions ( -1) F- Fluoride NO- Nitrate I- Iodide C2H3O2- Acetate OH- Hydroxide MnO4- Permanganate Cl- Chloride CN- Cyanide ClO- Hypochlorite Br- Bromide ClO2- Chlorite BrO3- Bromate ClO3- Chlorate HCO3- Hydrogen Carbonate

Common Anions (-2) O-2 Oxide S-2 Sulfide SO4-2 Sulfate CO3-2 Carbonate Cr2O7-2 Dichromate CrO4-2 Chromate

Common Anions (-3) N-3 Nitride P-3 Phosphide PO4-3 Phosphate

Chemical Formulas and Units A chemical formula shows the kinds of atoms in the molecule as well as the amount of atoms in the molecule A formula unit is expressed in the smallest whole number ratio for the molecule Examples: NaCl TiO2 VCl5 Ca3(PO4)2

Ionic Bonding The single most important thing about ionic bonds = ELECTRONS ARE EXCHANGED Ionic bonds occur between a METAL and a NONMETAL (Cation and Anion) High Boiling Point High Melting Point Good Insulator (Solid) Good conductor Liquid (Melted) or Aqueous Aqueous = Dissolved

Ionic Bond Characteristics Explained Compounds of ionic bonding are often solid at room temperature Ionic compounds will have a lattice structure or a 3D crystalline shape The structure is responsible for: High melting points High boiling points Insulating Solid (electrons are stored) Conductive liquids and solutions (electrons are free)

Binary Ionic Compounds A Bicycle has how many wheels? A biplane has how many wings? A binary compound has how many elements? A binary ionic compound has two elements where electrons are exchanged NaCl MgBr2 Ca3N2 Sodium Chloride Magnesium Bromide Calcium Nitride

Polyatomic Ions What is polytheism? What is a polygon? How about polyatomic ions? Polyatomic ions are IONS that consist of multiple atoms Polyatomic ions are used in ionic bonding because there is still an exchange in electrons

Covalent Bonding The single most important thing about covalent bonds: ELECTRONS ARE SHARED Covalent Bonds occur between a NONMETAL and a NONMETAL Low Melting Point Low Boiling Point Poor Conductivity Polar Nature Usually liquids and gases at S.T.P. Standard Temperature and Pressure

Covalent Bonding Explained Bonds can occur as single, double, or triple bonds Each bond represents a PAIR (2) of electrons Best represented in diatomic molecules (F, Cl, Br, I, H, N, O) Lewis Dot Diagram helps determine where a double or triple bond can occur Polarity is a result of unequal distribution of electrons ∴ the bond creates a positive end (pole) and a negative end (pole) Covalent Bonds are the root of Organic Chemistry

Covalent Bonding VSEPR Theory Valance shell electron pair repulsion theory Predicts the shape of a molecule (covalent compound) Lone pair on the central atom push the ligands together altering the bond angles between the ligands Practice: CHI3, CO2, NH3, CH2O, SO3, HCN

VSEPR Shapes

Covalent Naming Name is determined by the number of atoms in the molecule MUST be covalent CO2, SO3, O3, C3O6

May the Force Be with You London Dispersion / Van Der Waals Forces Weakest – electrons of one compound attracted to the nucleus of another Includes compounds with non-polar forces Increases as the number of electrons increases Dipole-Dipole Forces Next strongest Between compounds that are polar Increases as mass increases Hydrogen bonding (The super dipole force) Attraction between molecules: H-F, H-N, H-O

Properties of Intermolecular Forces Viscosity – the measure of a fluids ability to flow Greater forces = greater resistance to flow Inverse relationship with temperature Surface Tension – energy required to increase the surface area of a liquid Increases with stronger dipole-dipole Water is an excellent example Capillary Action – ability of a liquid to flow against gravity Cohesion – Attraction within liquid Adhesion – Attraction to container

Transition Metals Transition metals have empty orbitals available for electron movement This movement results in multiple cations Cations can be predicted using electron notation Let’s look at copper!

Transition Metal Cations

Metallic Bonding Occurs between METAL and METAL Electron ”sea” develops when metals lose their electrons This “sea” gives the metals unique properties because the electrons are free to move at will The ”sea” is strong, but easily influenced by other atoms with high electronegativity

Characteristics of Metallic Bonds High Melting Point – Sea and heavy atoms High Boiling Point– Sea and heavy atoms High Conductivity – Electrons are free to flow Malleability – Ability to pound into sheets due to free moving electrons, no bonds Ductility – Ability to stretch into a wire due to free moving electrons, no bonds Luster – shiny appearance, free electrons are reflecting the light

Determining the Bond Use the electronegativity trend If they are close = covalent If they are far = ionic If they are both metals = metallic If there are multiple atoms that are close and far = covalent and ionic

Ionic Covalent Metallic NaCl NaNO3 CO4 Ag2CrO4 K2O N2O2 Fe2O3 TiC PCl5 What would the bond be? NaCl NaNO3 CO4 Ag2CrO4 K2O N2O2 Fe2O3 TiC PCl5 CuZn Ionic Covalent Metallic