Why is the size of cation smaller then its parent atom?

Explanation

Cation is formed when an electron is removed from the gaseous neutral atom. The number of electrons around the nucleus decreases. As a result, remaining electrons will feel larger attraction towards the nucleus. So, they will come more closer to the nucleus. Therefore, size of cation will decrease.
For example, `underset((231"pm"))Ktounderset((133"pm"))K^(+)+e^(-)`