题目

完形填空Yuan Longping, a Chinese scientist and educator,died at the age of 91 in Hunan last month. He was called the Father ofHybrid Rice（杂交水稻）and he helped 1 people around the world. Yuan Longping was the first person to develop a kindof hybrid rice which helped fight 2 in China. Food was a big problem in China inthe past. This was because China had 22 percent of the world's population, butonly 7 percent of its 3.In the 1960s, Chinese people had a difficult time. Millions of people diedbecause they had no food. As an agronomy teacher, Yuan was very 4tosee this. How can I help 下表为元素周期表的一部分，列出8种元素在周期表中的位置。用化学用语回答下列问题：⑴8种元素中，原子半径最小的是____，原子半径最大的是____，组成物质性质最稳定的是_____。⑵由⑤组成的单质存在同素异形现象，所组成的同素异形体有：_________；⑶⑥、⑦两种元素最高价氧化物对应的水化物中，碱性由强到弱的的是__________。⑷元素⑧的氢化物的化学式为__________。该氢化物的主要用途：用作试剂、航空燃料。写出该氢化物在空气中燃烧的化学方程式为____________。