A Se ion has a mass number of 77 and a charge of −2

Question

Accepted Answer

hey everyone in this example, we need to complete the below table by providing the missing information. We want to recall a few facts before filling things in. We should recall that for a neutral element we have our number of protons or our atomic number. Sorry, that should be equal to our number of protons. Which is also going to equal our number of electrons. We also want to recall that a positive ion charge means that we will lose electrons. Whereas a negative ion charge means that we will gain that number of electrons based on the charge. So for our first row here Or rather our first column we have the net charge of -2. And so if we know according to our first column that are neutral atom contains protons, that means that this minus two charge means we will have gained two more electrons on top of those 34 protons or 34 electrons. That would also be present in a neutral atom. And so we would have 34 plus two, which means we would be able to fill in 36 electrons in our blank here. And so we would refer to our periodic tables to see that the atomic number which is equal to our number of protons. So we want to find the atomic number 34 on our periodic tables. And we see that that corresponds to the atom selenium which also has atomic number 34 located in Group six A across period four of our periodic tables. And for our symbol of selenium, we want to go ahead and write in the mass number in the left hand superscript. So we would have the mass number 79 according to our atomic mass for selenium on our periodic tables. And then we would put in that ion charge which is a two minus ion charge. So moving on to our next column, We're told that our neutral atoms should have 20 protons which would correspond to the atomic number 20. When we look for atomic number 20 in our periodic tables, we see that that corresponds to the atom calcium. Now we should recognize that because we only have 18 electrons. This means that we do not have a neutral atom for our symbol here. And that's due to the fact that if it were a neutral atom we would have our number of protons equal to our number of electrons as well. So because we went down by two units to get electrons, we would say that we must have lost electrons meaning we must have a positive to charge. And so to fill in the rest of our symbol, we would see that calcium in group two a across period four of our periodic tables has a mass number of 40 according to its atomic mass given in the periodic table. And we'll have a plus two caddy on charge. Or we can just say two plus. So moving on to our next column, we have the Catalan lead four plus with the Atomic Mass 207. Now for a neutral atom of lead we would have the number of protons correspond to its position on the periodic table, which is its atomic number located in group four a across period six, which is atomic number 82. So we would say that in a neutral atom of lead we would have 82 protons. However, because we see that we don't have a neutral atom of lead, we have a four plus charge. That means of our 82 electrons, that would be in a neutral atom with 82 protons. We lose four electrons based on that four plus charge. And so we would take four minus eight or 82 minus four based on that four plus charge to give us 78 electrons. Next, we want to recall the fact that if we take our mass number And subtract that from our number of protons, that is going to give us our number of neutrons for our given Adam. And so to find the third column blank here for neutrons. We would go ahead and take our mass number of lead which is and subtract that from our 82 protons in a neutral atom of lead to give us the difference of 1 25 neutrons. And so we would fill that in As 1 25 here. So moving forward to our last column were given a plus seven net charge for an atom with 30 neutrons and 18 electrons. So because we see that we have 18 electrons and a net charge of plus seven, we would recognize that that means we lost seven of our original number of electrons in a neutral atom. And so we would go ahead and have 18 plus seven, which is going to give us a value of 25. And this tells us that 25 would have been our number of protons if our atom was neutral because we did recall that our mass number is equal to our number of protons plus neutrons. If we reorganize this formula here, We would be able to say that we have our 30 neutrons plus our 25 protons Which is going to equal a value of 55. And this is our mass number or atomic mass of our simple here. So we want to find our atomic number 25 on our periodic tables and we see that that would correspond to the Atom Manganese. We have a plus seven charge as given in the question here or in the column here. And we last want to go ahead and fill in that mass number of 55 which we found from adding our number of protons to our number of neutrons. And this will complete this example as our final answer of our field in chart based on the provided information. So I hope that everything I explained was clear. If you have any questions, please leave them down below, and I will see everyone in the next practice video.

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A Se ion has a mass number of 77 and a charge of −2

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