Just pondering: why doesn't the atomic mass go up in equal amounts with each proton?

Yes, it is because of the mass of neutrons. Neutrons and protons have an almost identical mass, but one or more is (almost) always added for each proton added.

The reason why atomic mass is so often fractional is because they take the average of all the possible different variations of the atom with different masses, and different amounts of neutrons.

Because of the changing numbers of neutrons in the nucleus :). Its only the atomic number which goes up in 1s, the average number of neutrons in a nucleus is less linear.

And by the way, all protons weigh exactly the same :)

Simple answer is yes-the neutrons. Can find the number by atomic mass-atomic number. The decimals in the mass are because there are different isotopes (different #'s of neutrons), averaged out.

The masses that are listed on your periodic table shower curtain are the average masses of the elements given their isotopic distribution.

So for example, although we say, on average, that the mass of hydrogen is 1.0079 g/mol. But really, the mass is 1.0078 g/mol (99.98% naturally abundant) and 2.014 g/mol (0.02% abundant). The different mass of the two isotopes is a result of the extra neutron for the heavier isotope.

Taking into account the natural abundance of each isotope of hydrogen, one arrives at the listed mass of hydrogen seen on your shower curtain, 1.0079 g/mol. What you see on your curtain is effectively a weighted average of the mass of a particular element. This is how we arrive at masses that are not multiples of one, as you stated by the addition of a proton for each subsequent element.

Oh dear, the difference in mass is due to the additional number of neutrons added to it. the mass of a neutron is approximately equal to that of a proton

the atomic mass on your periodic table is not based on just one atom name on it.

like atomic mass of hydrogen is 1

'1' is not the mass of hydrogen atom only

but it is the average mass of hydrogen's isotopes

which is H-1, H-2, H-3

so. even one proton can change a lot of the mass of the atom in the periodic table.

(hydrogen has 3 isotopes, chlorine has 2 isotopes, etc)

masses that you see on your periodic table is already simplified by those smart 'chemistry' people.

it's one of the reason why it's change a lot.

---hope it helps :D

the respond is 4 - proton and neutron. a positron is the anti-count equivalent particle to an electron, which has the comparable mass yet an excellent fee extremely of a unfavourable one. in spite of the undeniable fact that all of us comprehend it exists, it generally has no function in our every day lives.