I think the answer is ‘repulsion’
The molar<span> volume of an ideal gas is therefore 22.4 dm</span>3<span> at </span>stp<span>. And, of course, you could redo this calculation to find the volume of 1 mole of an ideal gas at room temperature and pressure - or any other temperature and pressure.</span>
Answer:

Explanation:
Hello.
In this case, since the undergoing chemical reaction is only between the sodium bicarbonate and the acid HA:

For 0.561 g of yielded carbon dioxide (molar mass 44 g/mol), the following mass of sodium bicarbonate (molar mass 84 g/mol) that reacted was:

Considering the 1:1 mole ratio between CO2 and NaHCO3. Finally, the percent by mass of NaHCO3 is computed by dividing the mass of reacted NaHCO3 and t the mixture:

Best regards.
Answer:
I don't know 100% but im pretty sure its electrons, if im wrong im really sorry let me know in the comments ill change it
explanation
the nucleus has more weight but its more compact but the electrons are spread apart circling the nucleus and therefor take up more space