Question

Why are there no atoms of elements that have masses as stated on the periodic table?

Answer 1

Because of the existence of isotopes.

Step-by-step explanation:

Let's look at the simplest atom, hydrogen. The majority of hydrogen atoms are the

1

H

isotope; their nuclei contain the 1 proton, the one positively charged nuclear particle. A few hydrogen nuclei contain the 1 proton (this is of course what defines them as hydrogen atoms), but also 1 neutron in addition, to give the deuterium,

2

H

, isotope; a smaller fraction of hydrogen nuclei contain 2 neutrons, to give the tritium isotope,

3

H

.