Atomic mass / mass number / atomic weight
(all of which mean the same thing)
2H2O = 2H2 + O2.
<h3><u>Explanation</u>:</h3>
Balancing equations is very essential because of the fact that it represents the stoichiometric quantities of the reactants needed to react to form the product. The ratio of the weights of reactant and product are also very well understood from this.
Here in this equation, the water is broken into hydrogen and oxygen. The balanced reaction is
2H2O = 2H2 + O2.
Two moles of water is broken down into 2 moles of hydrogen and one mole of oxygen.
Answer:
Isotopes are basically atoms of an element that have an unequal number of neutrons and protons. Of course the proton number remains the same, but the neutron number either decreases or increases, which leads to an overall change in mass. However, no chemical properties of the atom/element are changed as the electrons are the same number and do not react. In regards to Helium 4, the original number of neutrons in Helium is 2, and protons 2 as well. We see an equal number of neutrons and protons, hence an unchanged mass, and the element is <em>not</em> an isotope.
All of these are compounds except oxygen because a compound is two or more different elements bonded together.