What kind of substance is made up of two or more elements chemically bonded together in a fixed mass ratio

Write the symbol for every chemical element that has atomic number greater than 3 and atomic mass less than 12.0 u.

An atom of sodium-23 (atomic number = 11) has a positive charge of +1. give this information, how many electrons does it have? how many proteins and neutrons does this atom have

Which of the following is the correct definition of chemical energy? a. energy an object has because of its motion or position b. energy resulting from the flow of charged particles, such as electrons or ions c. energy produced from the splitting of atoms d. energy stored in chemical bonds of molecules