电子绕原子核加速运动辐射电磁波使得原子不能稳定存在.本文假设电子在极短时间绕原子核做匀速圆周运动，依据经典电磁理论建立电子运动半径的微分方程，求解得到电子在极坐标系下的轨迹方程和掉落到原子核的时间表达式.计算结果表明电子围绕原子核做螺旋线运动，大约在10-10 s时间内掉落到原子核.

The accelerative motion of electrons around the nucleus radiates electromagnetic waves that make atoms unstable. In this paper, the differential equation of the radius of electron motion is established on the assumption that an electron moves in a uniform circle around the nucleus for a short time. The trajectory equation of electron in polar coordinate system and the time expression of electron falling to the nucleus are obtained. It is concluded that an electron moves in a spiral around atomic nucleus and falls to the nucleus in about 10-10 s.