Why did he call the atomic model proposed by Rutherford “planetary”?

Because it is very similar in structure to the solar system: the size of the sun (the “core” of the solar system) is very small compared to the size of the orbits of the planets (“electrons” of the solar system), but almost all the mass of the solar system is concentrated in the sun.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.