Objectives 1 • Identify characteristics in atoms involved in chemical bonding • Compare the physical and chemical properties of ionic and covalent compounds • Compare the arrangement of atoms in molecules, ionic crystals, polymers, and metallic substances
Vocabulary: define in your journal • Valence electrons • Electron dot structures • Octet rule • Ionic bond • Anion • Cation • Metallic bonds
Covalent bond • Structural formula • Unshared pairs • Double covalent bonds • Triple covalent bonds • Coordinate covalent bonds • Bonds • Bond dissociation energy • Resonance structures
Nonpolar covalent bond • Polar covalent bond • Polar bond • Polar molecule • Dipole • Van der Waals Forces • Dispersion forces • Dipole interactions • Hydrogen bonds
Van der Waals forces Consist of two kinds • Dispersion forces: weak force caused by the motion of electrons, increases with increasing electrons Seen in diatomic molecules, weak in fluorine and chlorine making them gases Stronger in bromine causing it to be a liquid
Dipole interactions: caused by attraction of polar molecules for each other; occurs between weakly positive and negative molecules Water is held together by the dipole interactions of adjacent oxygen (-) and hydrogen (+) atoms when water molecules come close together Hydrogen bonds (+) are strongest of dipole interactions
Notes: Handout I. COMPOUND: A. The Chemistry meaning:
Notes Materials made from atoms of two or more combined elements.
B. Compounds have properties that are unlike the elements that form them. Notes
Notes 1. Na (Sodium) is a silvery metal that reacts violently with water.2. Cl (Chlorine) is a green gas that can kill any animal.
Notes 3. Na + Cl NaCl (table salt)which we eat with little harm.
Interaction between atoms that results in the formation of a compound. Notes
B. CHEMICAL BOND: Strong attractive force between atoms or ions in a compound. Notes
Notes C. BOND ENERGY: Energy involved in the making and breaking of chemical bonds.
Notes 1. Energy is released to make a bond.exothermic2. Energy has to be applied to break the bond. endothermic
Notes 3. The bond energy is the lowestpotential energy for the compound.
Notes 2. Ion - atom which has: a. Gained one or more electrons - negative charge (anion) b. Lost one or more electrons - positive charge (cation)
Quiz 1: Ionic and Covalent Bonds Draw a Lewis dot diagram showing the following bonds • An ionic bond forming calcium phosphide • A covalent bond forming carbon monoxide (make sure Carbon and Oxygen both have 8 valence electrons available to them)
Hybrid orbitals • Two overlapping orbitals form what is known as a hybrid or molecular orbital • Just as in a s,p,d, or f orbital the electrons can be anywhere in the orbital (even though the electron has started out in one atom, at times, it may be closer to the other nucleus) • Each hybrid orbital has a specific shape • You do not need to know shapes • You need to know that hybrid orbitals exist and that they are formed from overlapping orbitals
1s 1s 2s 2s 2p 2p 1s 1s 2p 2p 2s 2s 1s 1s 1s 2s Overlapping orbitals • Draw orbital diagrams for F+F, H + O, Li+F F2 H2O LiF is ionic (metal + non-metal)
Lewis diagrams Draw Lewis dot diagrams for Ne, Sb, Rb, F. How many variations of the Lewis diagram for P can be drawn? Ne Sb Rb F P P P P • Lewis diagrams follow the octet rule: atoms when forming ions, or bonding to other atoms in compounds have 8 outer electrons • Q - How can the octet rule be explained? • A - s (2 e–) and p (6 e–) orbitals are filled
e– 1) 2) Na Na+ Cl Cl– Cl– Na+ Ionic bonding • Recall: Ionic bonding involves 3 steps: 1) loss of e-, 2) gain of e-, 3) +ve, -ve attract 3) This can be represented via Lewis diagrams… • Diagram the reaction between Li + Cl and Mg + O (PE 3)
O [Mg]2+ [ O ]2– Mg Cl [Li]+ [ Cl ]– Li The octet rule (ionic compounds) • Draw Li + Cl and Mg + O (PE 3, pg. 230) • Note also that the charge on an ion can be determined by the number of places removed from a noble gas (Ca, N, Al?) • Ca2+, N3-, Al3+
Cl Cl C Cl Cl H H H H H Cl N H O [Mg]2+ [ F ]2– Covalent bonding • Covalent bonds can also be shown via Lewis diagrams - E.g draw Lewis diagrams showing the combination of 1) H+Cl, 2) C+Cl, 3) H+O, 4) Mg+F, 5) N+H, 6) Do PE 4 (pg. 234) H2O NH3 HCl MgF2 - Ionic CCl4 • Note bonds can also be drawn with a dash to represent two electrons
Notes E. COVALENT BONDS: Atoms share electrons rather than losing them
Notes 1. Usually between nonmetals2. Sharing can be unequal causing the compound to seem to have a charge.
a. One nucleus is larger(has more protons)and acts like a bigger magnet.(And because it has a higher electronegativity) Notes
b. The electrons spend more time around the larger nucleus than around the smaller nucleus. Notes