Answer:
The number of protons
<h2 /><h2>
Why does the number of protons determine the chemical element?</h2>
In a nutshell, the proton number defines the electric charge of the atom's nucleus and, because atoms are electrically neutral, it also determines the number of electrons.
The quantity and pattern of the electron distribution around the nucleus determine almost all, but not quite all, of the variations between the chemical elements. What truly counts for chemistry has a lot to do with how difficult it is to pull things off and other factors.
You may potentially argue that pure deuterium is a separate element than hydrogen in borderline circumstances when the number of neutrons does affect the electronic structure of the atom. One such example is the difference between hydrogen and deuterium. This is due to the fact that adding a neutron to a proton in hydrogen doubles the nucleus' mass, which alters the single electron's decreased mass.
However, the discovery of deuterium came quite late and solved a very old issue with measuring the density of water precisely. Numerous readings for this density at standard pressure and temperature did not agree with one another, despite the accuracy of the observations. The explanation for this anomaly turned out to be that there is actually a very little amount of deuterium mixed into regular water, and the density is actually based on where on Earth you collect the water sample and what you do with it.
But it found out that the varied isotopes of heavy elements that result from having more or less neutrons for every proton actually don't affect the chemistry all that much.
The idea that the isotope shifts are not significant for the heavier elements was, in my opinion, made quite forcefully and properly by Frederick Soddy, who collaborated with Rutherford. This was eventually addressed, and it is unquestionably the superior method to approach chemistry as a whole.
Even yet, there are still minute differences in the way the electrons organize themselves around the nucleus and the way the atoms move and interact with one another that are caused by the different neutron counts. However, this is not the major narrative.
Chemistry is a tale with amazing depth and richness because it is, in some ways, the story of where the electrons go and what they do when many various types of atoms combine.
Thank you,
Eddie
