（1）如图1是部分主族元素第一电离能梯度图，图中，a点对应的元素为氢，b、c两点对应的元素分别为　 ____　、　 ____　（填元素符号）．

（2）将CrCl₃•6H₂O溶解在适量水中得到深绿色溶液，溶液中Cr³⁺以Cr（H₂O）₅Cl²⁺形式存在．

①上述溶液中，不存在的微粒间作用力是　 ____　（填标号）．

A．离子键   B．共价键   C．金属键    D．配位键    E．范德华力

②Cr（H₂O）₅Cl²⁺中Cr³⁺的轨道杂化方式不是sp³，理由是 ____

（3）下面关于晶体的说法不正确的是　 ____　．

A．晶体熔点由低到高：CF₄＜CCl₄＜CBr₄＜CI₄

B．硬度由大到小：金刚石＞碳化硅＞晶体硅

C．熔点由高到低：Na＞Mg＞Al

D．晶格能由大到小：NaF＞NaCl＞NaBr＞NaI

（4）硼化镁晶体在39K时呈超导性．在硼化镁晶体中，镁原子和硼原子是分层排布的，图2是该晶体微观结构的透视图，图中的硼原子和镁原子投影在同一平面上．则硼化镁的化学式为　 ____　．

（5）铁的金属密堆积方式为体心立方结构，结构如图3所示．  则晶胞中铁原子的配位数为　 ____　．若铁原子的半径为r pm，写出该堆积方式的空间利用率的表达式（不要求算出结果）　 ____　．

完形填空

    Walt Whitman was a famous American poet (诗人). He was born 1 Mary 31, 1819, in Long Island. There were nine2 in his family, and he was the second. 3 he was four years old, his family moved to Brooklyn because his family was too poor. His childhood was restless (不安宁的) and unhappy. 4 the age of 11, he left school. Then he began to 5 a job to help his family. As a young man, Whitman 6 a school teacher, a printer and a newspaper reporter. He was 7 years old when he published his first book of poetry (诗集) in 1855. He 8 itLeaves of Grass. It 9 only twelve poems. The new form of his poetry 10 many people. Whitman was poor and weak during the last years of his life. He died in 1892.