
<u>Science is a systematic enterprise that builds and organizes knowledge in the form of testable explanations and predictions about the universe. The earliest roots of science can be traced to Ancient Egypt and Mesopotamia in around 3000 to 1200 BCE.</u>

So, to determine the number of neutrons in atom, we only have to subtract the number of protons from the mass number. Take note that the nucleus of an atom is composed of protons and neutrons. And the number of particles present in the nucleus is referred as mass number (Also, called as atomic mass).
CH4+2O2–>CO2+2H2O
4Fe+3O2–>2Fe2O3
Answer:
Cl is chloride I think, and NaCl is a salt molecule