Answer:
For any given isotope, the sum of the numbers of protons and neutrons in the nucleus is called the mass number. This is because each proton and each neutron weigh one atomic mass unit. By adding together the number of protons and neutrons and multiplying by 1, you can calculate the mass of the atom.
<span>The alkali metals and hydrogen are reactive because they have only one electron to give in order to complete their valence shell. It is easier to give that one electron so when given the opportunity they will. This means they will react with anything polar or willing to take an electron.</span>
Answer:
Law of Conservation of Energy
Explanation: