已知1～18号元素中的离子aX+、bY2-都具有相同的电子层结构，则下列关系的表示正确的是（ ）
A．离子的还原性：Y2-＜X+
B．a=b+3
C．原子半径：Y＞X
D．离子半径：Y2-＜X+
1～18号元素的离子aX+、bY2-具有相同的电子层结构，则核外电子数目相同，所以a-1=b+2，X处于Y的下一周期，由aX+、bY2-所带电荷可知，X处于第ⅠA则，Y处于第ⅥA族，
A．X+只表现氧化性，Y2-具有还原性，故还原性Y2-＞X+，故A错误；
B．aX+、bY2-具有相同的电子层结构，则核外电子数目相同，所以a-1=b+2，即a=b+3，故B正确；
C．X处于Y的下一周期，且X处于第ⅠA则，Y处于第ⅥA族，故原子半径X＞Y，故C错误；
D．aX+、bY2-具有相同的电子层结构，核电荷数越大离子半径越小，核电荷数b＜a，所以离子半径Y2-＞X+，故D错误；
故选B．
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| Our neighbour's son was getting married in 2009 at an out-of-town church, and my husband and I were invited. We immediately rushed out to a 1 , and I bought a nice pink dress with a jacket. The dress was a little 2 , but I had a month to go before the June 30 wedding and I would 3 a few pounds. June 29 came and, of course, I hadn't lost a single pound; in fact I had 4 two. But I 5 a nice new girdle (紧身内衣) would cure everything. So on our way out of the city we 6 once again at the store. I ran in and told the clerk I needed a 7 large girdle. The clerk found the box with the 8 girdle marked "LG", and asked if I would like to try it on. "Oh, no, a large will fit just right. I 9 try it on." The next morning was rather hot, one of those thirty-four degree days, I suppose, so I 10 to get dressed until about 45 minutes before time to go. I opened the box only to 11 a new girdle in a small size. Since it was too late to find another one and the dress wouldn't 12 right without a girdle, a fight 13 in the hotel room between me and the girdle. Have you ever tried to 14 20 pounds of potatoes into a five-pound bag? That's it. Finally my husband, 15 like crazy, got hold of each side and shook me down into it. At once I put on the pink dress, which didn't 16 very well with my red face, and was ready to go. Finally we got to the 17 . I heard one of the people say that they were having a High Mass (大弥撒). I turned to my husband and asked, "What is a High Mass?" He shrugged his 18 . 19 , I learned that this particular mass would last one hour, twenty-two minutes and eight and one half seconds-the priest (神父) was going to bless 20 except my girdle. | ||||
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