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Welcome back everyone. Which of the following is the correct number of protons neutrons and electrons in an atom of Mercury 199. So we should recall that when we have a symbol of an isotope. We have the mass number written in the left hand subscript A. We have its atomic number written written in the left hand. We're sorry left hand exponents is our mass number A. And our left hand subscript is our atomic number Z. Here. So recall that our mass number is described by our number of protons added to our number of neutrons. And to get our number of protons, we look to our atomic number and we see that this describes our number of protons and our number of electrons. So number of electrons. But this is only true for neutral atoms only, meaning we shouldn't have a charge on our atom or our element. So looking at our mercury 1 99 isotope, we can see we don't have a charge in the formula or in the symbol rather. And so this means that we have a neutral isotope. So riding out this isotope symbol larger, we have mercury 199 With the atomic number of Where we would recognize based on this atomic number 80, that we have 80 protons. And as we stated, this is a neutral isotope. And so therefore we have 80 electrons. So so far, we've confirmed that we have 80 electrons and 80 protons and now we just need to determine our number of neutrons, which we would recall. We can find by taking the difference between our mass number of 1 99 minus r protons. And this difference gives us our number of neutrons equal to 119 neutrons, which would be our third amount of our subatomic particle neutron. So our only correct final answer is going to be choice A 80 protons, 80 electrons and 119 neutrons are present in our isotope of mercury 99. I hope everything I reviewed was clear. If you have any questions, leave them down below and I'll see everyone in the next practice video.

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