题型:选择题 Shelly had prepared carefully for her biology examination so that she could be sure of passing it on her first ____. [ ]A. attraction B. attempt C. arrival D. article 查看答案
题型:选择题 已知,aAn+、bB(n+1)+、cCn-、dD(n+1)-具有相同的电子层结构,关于A、B、C、D四种元素的叙述正确的是[ ]A.气态氢化物的稳定性:D>C B.原子序数:B>A>C>D C.最高价氧化物对应水化物的碱性:B>A D.四种元素一定属于短周期元素 查看答案