Mass number<span> is the </span>number<span> of protons </span>and<span> neutrons in an atom.
</span>Atomic mass<span> is the average </span>mass<span> of all the isotopes of a certain type.</span>
For 23., you have to find a way to measure your heart rate not increase it. search it up on google.
francium , in the Periodic table the atomic radius increases from top to bottom in a group, and decreases from left to right across a period. making helium is the smallest element, and francium the largest.
