15.1 氧族元素的通性 本章内容 15.2 氧及其化合物 Oxygen and it's some important compounds 15.3 硫及其化合物 Sulfur and it's some important compounds 15.4硒和碲（不要求） Selenium and Tellurium15.1 氧族元素的通性 15.2 氧及其化合物 Oxygen and it’s some important compounds 15.3 硫及其化合物 Sulfur and it’ s some important compounds 15.4 硒和碲 (不要求) Selenium and Tellurium