Is the trend for ionic radius just that for metals, they are smaller than the nuetral atom and for non-metals, and for non-metals, they are bigger than the neutral atom?
Or is there another specific trend?
The trend for ionic radius is actually more nuanced than just distinguishing between metals and non-metals. In general, the ionic radius refers to the size of an ion, which can be either positively or negatively charged.
For cations (positively charged ions), such as metal ions, the ionic radius is smaller than the neutral atom. This is because cations form when an atom loses one or more electrons. When electrons are removed, the remaining electrons experience increased electrostatic attraction from the positively-charged nucleus, causing the electron cloud to contract and thus reducing the size of the ion.
On the other hand, for anions (negatively charged ions), such as non-metal ions, the ionic radius is larger than the neutral atom. Anions form when an atom gains one or more electrons. By adding electrons, the electron-electron repulsion increases within the electron cloud, causing it to expand and leading to an increase in the size of the ion.
It's important to note that the trend of ionic radius also varies within specific groups and periods of the periodic table. Generally, as you move down a group (vertically), the ionic radius increases due to the addition of new electron shells. Conversely, as you move across a period (horizontally), the ionic radius generally decreases as a result of increased nuclear charge pulling the electrons closer.