Which type of nuclear energy involves splitting atoms

That would be nuclear fission. This occurs at a rapid level in the Atom Bomb. That is a chain reaction causing an explosion whereas the nuclear fission that occurs in a nuclear reactor is controlled.

each chemical family is represented as a group or column on the periodic table. based on chemical properties, there are 6 types of chemical families. group 1 represents alkali metals, group 2 represents alkaline earth metals, groups 3 to 12 represent transition metals, groups 13 to 16 represent non-metals and other metals, group 17 represents halogens and group 18 represents noble gases.