Metalloid

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