plutonic rocks are formed when magma cools and solidifies underground This shows us if the rock is plutonic or volcanic. When magma cools underground, it cools super slow and when lava cools above ground, it cools faster. When magma and lava cool, mineral crystals start to form in the molten rock.
Because the Potassium ion loses an electron, the electrons come a little closer to the nucleus because they are attracted to the protons. This makes the ion smaller in radius