问题 填空题

W、X、Y、Z四种短周期元素的原子序数X>W>Z>Y。W原子的最外层没有p电子,X原子核外s电子与p电子数之比为1∶1,Y原子最外层s电子与p电子数之比为1∶1,Z原子核外电子中p电子数比Y原子多2个。

(1)X元素的单质与Z、Y所形成的化合物反应,其化学方程式:________________________。

(2)W、X元素的最高价氧化物对应水化物的碱性强弱为__________<__________(用分子式表示)。

(3)这四种元素原子半径的大小为__________>__________>__________>__________(填元素符号)。

答案

(1)2Mg+CO22MgO+C

(2)Mg(OH)2<NaOH

(3)Na>Mg>C>O(说明:顺序全对才给分)

Y原子最外层s电子与p电子数之比为1∶1,可能为1s22s22p2或1s22s22p63s23p2;X原子核外s电子与p电子数之比为1∶1,可能为1s22s22p4或1s22s22p63s2,考虑到W、X、Y、Z四种短周期元素的原子序数X>W>Z>Y,X、Y应为1s22s22p2、1s22s22p63s2,即分别为镁和碳;Z原子核外电子中p电子数比Y原子多2个,Z为氧元素;W原子的最外层没有p电子,应为钠。同一周期,元素的最高价氧化物对应水化物的碱性减弱,所以,Mg(OH)2<NaOH,元素周期表中的同周期主族元素从左到右,原子半径逐渐减小,同主族元素从上到下,原子半径逐渐增大,因而Na>Mg>C>O。

选择题
填空题

Holidays are special times of (1) from work and other routines. Holidays are often times for celebration, (2) , eating, drinking, travel, and family (3) . In most cultures the scheduling of holidays originally was related to the (4) , the (5) cycle, and (6) . Christmas, December 25, celebrates the (7) of Jesus, but it is not actually known whether Jesus was (8) in the wintertime Over the years Christmas has come to symbolize goodwill and (9) for both Christians and non-Christians, and the (10) of Christmas threatens to replace generosity with greed. Other important holidays in America are Valentine’s Day, St. Patrick’s Day, April Fools’ Day, and (11) . On Valentine’s Day, people give cards, chocolates, flowers, and kisses to their (12) and sweethearts. During Easter Week in late March or early April, Christians remember the death and (13) of Jesus. Although not actually a holiday and has no religious (14) , April Fools’ Day, celebrated on April 1, is a day when people play embarrassing (15) on their fiends and (16) and even on their teachers. In (17) , Labor Day is celebrated on May 1, whereas in (18) and the United States, labor and laborers are honored by a (19) holiday on the first (20) in September.

Holidays are special times of (1) from work and other routines. Holidays are often times for celebration, (2) , eating, drinking, travel, and family (3) . In most cultures the scheduling of holidays originally was related to the (4) , the (5) cycle, and (6) . Christmas, December 25, celebrates the (7) of Jesus, but it is not actually known whether Jesus was (8) in the wintertime Over the years Christmas has come to symbolize goodwill and (9) for both Christians and non-Christians, and the (10) of Christmas threatens to replace generosity with greed. Other important holidays in America are Valentine’s Day, St. Patrick’s Day, April Fools’ Day, and (11) . On Valentine’s Day, people give cards, chocolates, flowers, and kisses to their (12) and sweethearts. During Easter Week in late March or early April, Christians remember the death and (13) of Jesus. Although not actually a holiday and has no religious (14) , April Fools’ Day, celebrated on April 1, is a day when people play embarrassing (15) on their fiends and (16) and even on their teachers. In (17) , Labor Day is celebrated on May 1, whereas in (18) and the United States, labor and laborers are honored by a (19) holiday on the first (20) in September.