问题 填空题

(8分)元素A、B、C都是短周期元素,A元素原子的2p轨道上只有两个未成对电子,B的3p轨道上有空轨道,A、B同主族,B、C同周期,C是本周期中电负性最大的。请回答:

(1)A原子的核外电子排布的轨道表示式________,B原子的核外电子排布式__________________,C原子的价电子排布式________。

(2)A、B、C的气态氢化物中最不稳定的是________(填化学式)。

(3) A、B、C的最高价氧化物的水化物中,酸性最强的是________。

(4)AC4的结构式为________,中心原子A的杂化方式________杂化,是________(填“极性”或“非极性”)分子。

答案

(1)  1s22s22p63s23p2;3s23p5 (2)SiH4 (3)HClO4

(4);sp3;非极性

题目分析:元素A、B、C都是短周期元素,A元素原子的2p轨道上只有两个电子,则A的外围电子排布为2s22p2,故A为碳元素;B的3p轨道上有空轨道,则B的A的外围电子排布为3s23p1或3s23p2,A、B同主族,故B为硅元素;B、C同周期,C是本周期中电负性最大的,故C为氯元素,则

(1)A为碳元素,碳原子的;B为硅元素,Si原子的核外电子排布式为1s22s22p63s23p2;C为氯元素C原子的核外电子排布式为1s22s22p63s23p5,价电子排布式为3s23p5

(2)C为氯元素,最低负价为-1价,气态氢化物的化学式是 HCl;非金属性越强,氢化物越稳定,非金属性Cl>C>Si,所以氢化物稳定性HCl>CH4>SiH4,气态氢化物最不稳定的化学式是SiH4

(3)非金属性越强,最高价氧化物的水化物酸性越强,非金属性Cl>C>Si,所以酸性HClO4>H2CO3>H2SiO3,酸性最强的是 HClO4

(4)AC4的化学式CCl4,分子中碳原子与氯原子之间形成1对共用电子对,结构式为,中心原子C原子的杂化轨道数为4,碳原子采取sp3杂化,分子为正四面体对称结构,是非极性分子。

单项选择题

A few years ago I had an "aha!" moment regarding handwriting.

I had in my hand a sheet of paper with handwritten instructions on it for some sort of editorial task. It occurred at first that I did not recognize the handwriting, and then I realized whose it must be. I finally became aware of the fact that I had been working with this colleague for at least a year, maybe two, and yet I did not recognize her handwriting at that point.

It was a very important event in the computerization of life—a sign that the informal. Friendly communication of people working together in an office had changed from notes in pen to instant messages and emails. There was a time when our workdays were filled with little letters, and we recognized one another’s handwriting the way we knew voices or faces.

As a child visiting my father’s office, I was pleased to recognize, in little notes on the desks of his staff, the same handwriting I would see at home in the notes he would leave on the fridge—except that those notes were signed "dad" instead of "RFW".

All this has been on my mind because of the talk about The Rise and Fall of Handwriting, a book by Florey. Sire shows in her book a deep concern about the fall of handwriting and the failure of schools to teach children to write well, but many others argue that people in a digital age can’t be expected to learn to hold a pen.

I don’t buy it. I don’t want to see anyone cut off from the expressive, personal associations that a pen still promotes better than a digital keyboard does. For many a biographer, part of really getting to know their subjects is learning to read their handwriting.

What some people advocate is teaching one of the many attractive handwritings based on the handwriting of 16th century Italy. That may sound impossibly grand—as if they want kids to learn to draw by copying classical paintings. However, they have worked in many school systems.

People working together in an office used to ().

A.talk more about handwriting

B.take more notes on workdays

C.know better one another’s handwriting

D.communicate better with one another

单项选择题