短周期元素X原子核外的电子处于n个电子层上，最外层电子数为（2n+1），核内质子数为（2n2－1）。有关X的说法中不正确的是
A．X元素气态氢化物的水溶液不可能呈酸性
B．X能形成化学式为NaXO3的含氧酸钠盐
C．X原子的最外层电子数和核电荷数不可能为偶数
D．X元素常见单质的化学式为X2
答案：A
题目分析：短周期元素X有n个电子层，所以若n分别等于2或3，则满足条件的元素为N、Cl元素，所以X元素的氢化物可能是NH3和HCl，所以A错误；X能形成化学式为NaXO3的含氧酸钠盐分别为NaNO3、NaClO3 ，B正确；最外层电子数和核电荷数不可能是偶数，C正确；两种元素的常见单质均是双原子单质，D正确；故选B。
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