C:20983Bi和21083Bi的核外电子数相同,中子数不同
A:20983Bi和21083Bi是同一种核素
B:20983Bi和21083Bi都含有83个中子
D:20983Bi和21083Bi分别含有126和127个质子
John can't go to the party on Thursday because he to go out on school nights.
宇航员在某星球表面让一个小球从高度为h处做自由落体运动,经过时间t小球落到星球表面.已知该星球的半径为R,引力常量为G.不考虑星球自转的影响.求: