How many neutrons and protons in the isotopes ""^(25)Al, ""^(95)Tc, and ""^(120)Sn?

Aug 13, 2017

Have you got a Periodic Table beside you?

Explanation:

And if the answer is no then amend this deficiency pdq. The Periodic Table classifies all the 100 or known elements on the basis of their atomic number $Z$. $Z$ represents the number of charged, massive particles, i.e. protons, present in the element's nucleus: $Z = 1$, the element is hydrogen; $Z = 2$, the element is helium;
$Z = 3$, the element is lithium;...........$Z = 26$, the element is iron; etc.

In the neutral particle, $Z$ also represents the number of electrons, fundamental particles of negligible mass that are conceived to whizz about the nuclear core. Transfer of, and sharing of electrons between nuclei give rise to all of chemistry.

Now we know the nuclear core contains protons, fundamental positively charged particles. They can also contain NEUTRONS, massive nuclear particles of ZERO electric charge, and this gives rise to the phenomenon of isotopes. For example, if a nucleus contains 1 proton, then by definition $Z = 1$, and we have the hydrogen element. However, the nucleus can also contain various numbers of neutrons which add to the atomic mass: i.e. $\text{^1H,"protium}$, $\text{^2H,"deuterium}$, $\text{^3H,"tritium}$; i.e. these are various hydrogen isotopes.

As nuclei get larger, the element can support greater numbers of stable isotopes, and the quoted atomic mass on the Periodic Table is the WEIGHTED average of these isotopes.

So we have covered all of chemistry and physics. Finally, we get to your question. You gots ""^25Al; a glance at the Periodic Table, tells me that for $A l$, $Z = 13$; the nucleus thus contains 13 protons, and NECESSARILY (why) 12 neutrons.

For ""^95Tc, $Z = 43$, therefore we gots 52 neutrons. Agreed?

For ""^120Sn, $Z = 50$, therefore we gots 70 neutrons.

I will let you do the last isotope, ""^200Hg. Please put the answer below. Remember you are wasting your time in this exercise if you DON'T got a Periodic Table in front of you. Is there?