The atom can be broken down into smaller parts. what are the smaller parts? how are atoms of hydrogen identical to each other, and how can they be different from each other? how are atoms of hydrogen different from atoms of helium? how can atoms be similar to atoms? how is water different from hydrogen peroxide even though both compounds are composed of only hydrogen and oxygen? what happens in a chemical reaction, and why is mass conserved in a chemical reaction?

The mass of an atom comes from the protons and neutrons that are found in the nucleus. The number of protons is the atomic number of an element. To find the number of neutrons, subtract the atomic number from the mass of an atom. The number of atoms of an individual element be determined by using a chemical formula and adding all of the subscripts together after the reaction is complete. The key in the balancing of chemical reaction is to make sure that you got the exact chemical formula of the substance that is reacting and the yielded product. After getting the formula, identify first the hardest element/atom to be balanced such as Na, Zn, Cl, C, O, etc. Then proceed to the easier ones such as O, H. Make sure to note the atoms present in the molecule of the substance.