how does the arrangement of atoms in most solids differ from the arrangement of atoms in a liquid?

Well, in solids the atoms are packed tightly together and so they have lesser freedom of movement and vibrate at their fixed positions. So the volume and shape of the liquid is definite.
In liquids, the atoms are more loosely/losely (4give my spelling) packed and have more spaces between them. The forces of attraction btwn a liquids atoms are relatively smaller than in a solids atoms.], and so the liquid ends up taking the shape of it's container ^^ , but a liquids volume is also definite and it can't be compressed.