碱土金属jiǎn tǔ jīn shǔ释义alkaline earth (i.e. beryllium Be 鈹|铍, magnesium Mg 鎂|镁, calcium Ca 鈣|钙, strontium Sr 鍶|锶, barium Ba 鋇|钡 and radium Ra 鐳|镭)单字详解碱jian土tu金jin属shu