X、Y两元素可形成X2Y3型化合物，则X、Y原子最外层的电子排布可能是( )。
A．X：3s23p1 Y：3s23p5
B．X：3s2 Y：2s22p3
C．X：3s23p1 Y：3s23p3
D．X：2s22p3 Y：2s22p4
答案：D
题目分析：X、Y两元素可形成X2Y3型化合物，则X、Y的常见化合价为+3、-2，即X元素容易失去3个电子达到稳定结构，Y元素容易得到2个电子达到稳定结构。选项中元素为第二、三周期元素，稳定结构均是最外层达到8电子。
点评：此知识点难度不高，考生应注意要遵循能量最低原理来书写电子排布式。掌握泡利不相容原理和洪特规则的内容是解题的关键。
| 完形填空 | ||||
| One day I pulled up to my apartment building and noticed there was a father and daughter __1__ some things from a moving truck.Normally I'm shy away from contact with __2__.That particular day, though,something was in me；I can't explain __3__,but I felt like I should just help these people,even __4__ something as seemingly unimportant as unloading a truck.So I __5__ and introduced myself, welcomed them to the town,and asked them to give me a(n)__6__ to put some proper shoes on.After I had flip－flops(夹趾拖鞋)on,I went over and helped them move all of their __7__ into the apartment. After we finished,we talked some and I got to know my new __8__.It might seem unimportant,but it seems like people are less __9__ and friendly to their neighbors these days；I wanted to __10__ that, at least in my small __11__ block.So we did talk,and they're from Florida,just like me. At that __12__ time in my life,I was going through a really difficult __13__ with my girlfriend of 7 years.I didn't feel like helping anyone or doing anything __14__,but I figured why not?And I'm glad I did. Also,as __15__ would have it,their daughter is my age(college student)and we each had a mutual(相互 的)__16__in one another.This developed into a friendship,and in the coming months,probably more. The __17__ was the act itself,though.I got to know my new neighbors and made some new friends in the __18__.And I felt really good about it.Since then,I've tried __19__ my comfort zone to perform other unplanned acts of __20__.So far,so good.I'd encourage everyone else to do the same! | ||||
|