Chapter 6B: Chemical Bonding General Chemistry Mr. Mata Cartoon courtesy of NearingZero.net

6-3 Ionic Bonding and Compounds Ionic Compound- composed of + and - ions combined so charges are equal. (Metal + nonmetal) Formula Unit- simplest group of atoms form an ionic compound.

Cation Formation Main group metals lose all their valence e-’s to form cations (+): This loss of electrons is called oxidation. Na . Na1+ + 1e- sodium Mg: Mg2+ + 2 e- magnesium : Al . Al 3+ + 3 e- aluminum

Anion Formation Non-metals gain e-’s to form anions (-). This process is called reduction. Cl 1- chloride (gain 1 e-) O 2- oxide (gain 2 e-’s) N 3- nitride (gain 3 e-’s)

Ionic Bond - charges are attracted to + charges. - anions are attracted to + cations. The result is an ionic bond. 3-D crystal lattice of anions & cations formed.

Structure of NaCl

Properties of Ionic Compounds Crystals form. High melting point & boiling point. Brittle (breaks easily). Melt when heated (very high temps!) Aqueous solutions conduct electricity. (solutions mixed in water)

Electronegativity (EN) Atoms to the right & top of Periodic Table have greater EN values. F most EN of elements (EN = 4.0). Fr least EN of elements (EN = O.7). Cl =3.0 H = 2.1 S = 2.5 O = 3.5 Na = 0.9 Br = 2.8 C = 2.5 N = 3.0 I = 2.5

Polar & Nonpolar Bonds H-H is non-polar because H & H have the same EN’s. (EN diff. = 0) Cl-Cl is non-polar because Cl & Cl have the same EN’s. (EN diff. = 0) H-Cl is polar because H & Cl have different EN’s. ( H = 2.1, Cl = 3.0 )

Predicting Bond Type There is a continuum between non-polar covalent bonds to ionic bonds. Non-polar bond; little difference in EN between atoms. (EN diff. = 0 – 0.3) Ionic bonds; greatest EN diff between atoms. (ΔEN > 1.7) Polar covalent bonds; in between EN diff between atoms. (EN diff. = 0.3 – 1.7)

Ionic vs. Covalent Bonds Sharing e-’s non-metal + non-metal Molecular (low mp/bp) ex: CO2, Cl2 Macromolecular (high mp/bp) Ex: C(diamond), SiO2 Non conductors Ionic Bonds Exchange e-’s Metal + non-metal 3-D units (crystals) high mp/bp Brittle, melt Ex: NaCl conduct electricity

Ionic Bonding in NaCl

Ionic Bonding in NaCl

6-4 Metallic Bonding Metals- conduct heat, have low ionization energy Low EN; give up electrons easily. Metals have luster (shine), are malleable (can be hammered into sheets) and are ductile (drawn into wires).

Metallic Bonding Metallic Bonding - type of bonding found in metallic crystals. 3-D lattice of positive ions. remain fixed in a crystal lattice. loosely-held valence e-’s move freely throughout the crystal. The fluid-like movements of valence e-’s make metals good conductors of heat and electricity.

Metallic Bonding

Metal Alloys Alloys -metallic substances composed of two or more elements; at least one of these elements is a metal. Alloys are important because the properties of an alloy are often superior to those of its component elements.

Chapter 6 SUTW Prompt Describe the different properties of ionic bonds and metallic bonds by describing how the electrons interact with each bonding type. Complete an 8-12 sentence paragraph using the SUTW paragraph format. Hilight using green, yellow, and pink. Due Date: Monday, October 16, 2017 (start of class)