Tissues are groups of similar cells that have a common function. An organ is a structure that is composed of at least two or more tissue types and performs a specific set of functions for the body. Many organs working together to accomplish a common purpose is called an organ system
1.atom 2.energy level 3.atomic number 4.compound 5.shell 6.electrons 7.molecule 8.atomic mass 9.neutrons 10.diatonic 11.proton