sizes of ions and atoms

[DCshoesGIRL]

How can I use the periodic table to identify the relative sizes of ions and atoms? If U know, let me know................thanx

[jeffy]

Hmm, just found this. It's amazing seeing how tiny Al³⁺ is compared with Cl^-. AlCl₃ seems weird now with a tiny Al attached to 3 Cl. Like a tennis ball holding on to 3 soccer balls.

[Kaitlin]

I'm confused with these sizes. Radius of H is 30 picometers in the first picture. Google says 1 picometer = 0.01 angstroms. That means the radius of H is 0.3 angstroms. But in the second picture carbon and silicon ions are smaller than this. That doesn't make sense because H has one electron 1s1 but Si4+ is 1s2 2s2 2p6 so it must be bigger.

[NanoMachine]

I'd say it's because Si has much more positive charge than H. (14 protons v 1 proton.) This extra charge pulls the electrons in Si⁴⁺ into a smaller volume than occupied by one electron orbiting the hydrogen nucleus