chap18notes - AP Chemistry A. Allan Chapter 18 - The...

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AP Chemistry A. Allan Chapter 18 - The Representative Elements: Groups 1A through 4A 18.1 A Survey of the Representative Elements A. Basic Trends 1. Metals tend to lose electrons and form cations 2. Nonmetals tend to gain electrons and form anions 3. Metalloids (semi-metals) have properties of both metals and nonmetals a. B, Si, Ge, As, Sb, Te, Po, At 4. Metallic character tends to increase as atomic number increases within a group B. Atomic Size and Group Anomalies (Anomaly = oddity) 1. Hydrogen vs. Other Group I Elements a. Very small, relatively high electronegativity (2.1) b. Forms covalent bonds with nonmetals - other Group I elements form ionic bonds with nonmetals 2. Beryllium vs. Other Group II Elements a. Small, electronegativity of 1.5 produces covalent bonds with many nonmetals (other group II's form ionic bonds) b. BeO is amphoteric, other group II oxides are basic (form hydroxides) in solution 3. Boron vs. Other Group III Elements a. Boron is a nonmetal/semimetal, all others are active metals 4. Carbon vs. Silicon (Group IV Elements) a. Carbon readily achieves the octet by forming π bonds with oxygen in CO 2 b. Silicon does not form π bonds with oxygen in discrete SiO 2 molecules (1) Si 3p orbitals do not easily overlap with oxygen 2p orbitals (2) Si forms interlocking SiO4 tetrahedra which make up the crystalline structure of quartz 5. Nitrogen and Phosphorus (Group V) a. Nitrogen forms a diatomic molecule with π bonds (N 2 ) b. Phosphorus forms aggregates based on the tetrahedral P 4 molecule (1) Single bonds (2) Large atoms = weak π bonds 6. Oxygen and Sulfur (Group VI) a. Oxygen forms a diatomic molecule with π bonds (O 2 ) b. Sulfur forms aggregates such as the cyclic S
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This note was uploaded on 09/28/2009 for the course CHEM 102 taught by Professor Freeman during the Spring '08 term at South Carolina.

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chap18notes - AP Chemistry A. Allan Chapter 18 - The...

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