问题
选择题
| He never used to swim in the river, he? |
A. wouldn't B. doesn't C. was D. did |
答案
答案：D
搜题请搜索小程序“爱下问搜题”
| He never used to swim in the river, he? |
A. wouldn't B. doesn't C. was D. did |
答案：D
下表是元素周期表的一部分，回答以下问题：
| 11Na 钠 22.99 | 12Mg 镁 24.31 | 13Al 铝 26.98 | 14Si 硅 28.09 | 15P 磷 30.97 | 16S 硫 32.06 | 17Cl 氯 35.45 | 18Ar 氩 39.95 | |
| 19K 钾 39.10 | 20Ga 钙 40.08 | … | ||||||
（2）17号元素原子的核外电子排布是
．
（3）由12号元素和17号元素可以形成的化合物的化学式是______．