1. Why a solid has a definite shape but a liquid does not.
2. Why negative ions are larger then their atoms
1. Solids have definite shape and definite volume because the molecules in solid are closely packed and in fixed positions. The molecules can vibrate but do not move around which keeps the shape and volume definite.
Liquids have no definite shape but definite volume because the molecules in liquid are not so closely packed and they have space between them. The molecules can move around and the forces of attraction between molecules is less as compared to solids, so the liquid takes the shape of the container and volume is definite.
2. The negative ion is larger than the original atom. ... This means with more electrons but the same number of positive protons, the size of the ionic radius will increase. When an atom has its electrons attracted to another atom it becomes a positive ion. The positive ion is smaller than the original atom.