* Loss of electrons: Metals form positive ions (cations) by losing electrons from their outermost shell.

* Reduced electron-electron repulsion: With fewer electrons, the remaining ones experience less repulsion. This allows the electron cloud to contract, pulling the electrons closer to the nucleus.

* Stronger nuclear attraction: Since the number of protons in the nucleus remains the same, the attraction between the positively charged nucleus and the remaining negatively charged electrons becomes stronger. This pulls the electrons closer, further shrinking the radius.

In summary: The loss of electrons in metal ion formation leads to a decrease in electron-electron repulsion and an increase in nuclear attraction, both of which contribute to a smaller atomic radius.