原子由______和______构成，其中原子核由______和______构成的，______带正电荷，______不带电．由于原子核所带的电量和核外电子的______，但______，因此原子不显电性．
原子由原子核和核外电子构成，其中原子核由质子和中子构成的，质子带正电荷，中子不带电．由于原子核所带的电量和核外电子的电量相等，但电性相反，因此原子不显电性．
故答案为：原子核，核外电子，质子，中子，质子，中子，电量相等，电性相反．
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| Mary Roda's parents came to New York from Australia. They lived in a tall building. A man named Donald Smith lived in the building, too. He 1 a. toy company. One day Donald gave Mary, the 4-year-old girl, a new _ 2 _She played with the toy and said, "This is fun ! " A few weeks later Donald gave her _ 3 _toy. She played with it. She said, "I am not 4 _this toy. It doesn't work." She was a (n) 5 little girl. Donald liked her honesty, and they became friends. For years Donald gave Mary new toys, and she gave him very good 6 about the toys. When Mary was thirteen years old, Donald 7 her a new ball. The ball had a balloon (气球) inside it. Mary wanted to fill the balloon with water. She wanted to paint the ball in crazy colors. She wanted to 8 rice or beans (豆子) in it to make it noisy.The company made these 9 Mary's ideas were a great success! The company 10 thousands of the balls. That Christmas Donald gave Mary a (n) 11 gift. He made her a vice - president (副董事长) of the toy company. 12 made $200, 000 a year. Her job was to see 13 the new toys were fun. She took a car from her school to her office. She worked for three or four hours a day at her job, 14 she had to do her homework. Mary was a busy teenager. She had 15 time to be with her family. Her parents taught her that working hard and doing her best is very important. Today Mary works at a college. The little vice - president with bright ideas helps students think about their future. | |||
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