What determines the order of placement of the elements on the modern periodic table?
(1) atomic number(2) atomic mass(3) the number of neutrons, only(4) the number of neutrons and protons

The order of placement of the elements on the modern Periodic Table is the atomic number. The answer is number 1. The rest of the choices do not answer the question above. Atomic mass gives the number of mass of an atom. 

smooth muscle is composed of involuntary muscles found within the walls of organs and structures such as the esophagus, stomach, intestines, and blood vessels. those muscles push materials like food or blood through organs. unlike skeletal muscle, smooth muscle can never be under your control.