Metals • Reaction with oxygen: When metal is treated with oxygen on heating they react together to give basic oxides. 4Na + O2→ 2Na2O • Reaction with Hydrogen: Metals like sodium, potassium, and calcium burn-in hydrogen and forms corresponding halides. 2Na + H2→ 2NaH (sodium hydride) 2K + H2→ 2KH (potassium hydride) • Reaction with acids: Most of the reactive metals like sodium, potassium and calcium react with dilute acid to form salts and hydrogen gas. Zn + 2HCl→ ZnCl2 + H2

Metalloids The elements that show the properties of both metals and non- metals are called metalloids. Examples of metalloids are arsenic, antimony and germanium. Metalloids possess the following characteristics: • They are a poor conductor of heat and electricity. • They possess metallic lustre. • They form alloys. • They are neither malleable nor ductile.