For each representation of a nucleus A through E, write the atomic symbol and identify which are isotopes.
a.

Question

For each representation of a nucleus A through E, write the atomic symbol and identify which are isotopes.

a.

Accepted Answer

Welcome back everyone. For the given nucleus representations provide the atomic symbol and identity of the isotopes. In choice. A it states that our atomic symbol for representation one is lithium eight for two is brill eight for three is lithium nine and for four is brill nine. Our isotopes are stated to be lithium eight and lithium nine as well as barium eight and barium nine. In choice B, it states that our atomic symbol for representation one is lithium eight for two is beri eight for three is lithium nine and for four is bellum nine. And it states that our isotopes would be lithium eight and beri eight as well as lithium nine and beri nine. Then in choice C it states that our atomic symbol for representation one is lithium 542 is brillion four for three is lithium six and for four is bellum five. Whereas our isotopes are stated to be lithium five and lithium six as well as beli four and brillion five. In choice D, it states that our atomic symbol for representation one is lithium five for two is beri four for three is lithium six and for four is Burrill five. And it states that our isotopes are just lithium five and Beri five. Now observing our given nucleus representations one through four, we also want to observe that our spheres that are colored red represent protons and our spheres colored blue represent neutrons. We can count in representation one, a total of four neutrons. Whereas we can count a total of three red spheres which would correspond to three protons. Let's recall that for isotopes, we have the same atomic number represented by the symbol Z. But we have different mass numbers represented by the symbol A. And recall that our mass number is calculated by the sum of protons plus neutrons for our atom. Now let's also recall that our number of protons tells us our atomic number for atom. So if we have three protons in representation, one, this will therefore tell us that our atomic number or Z value is equal to three. And this will correspond to our symbol being lithium because on our periodic table, atomic number three corresponds to our atom lithium. Now, to calculate our mass number A, we would take four of our neutrons plus our three protons to give us our mass number of seven. And so with this mass number, we can recall that in our chemical symbol for a or for our atomic symbol, we would place our mass number in the left hand exponent. So we would have seven in our left hand exponent. And recall that we placed the atomic number in this case, three in the left hand subscript. So so far for representation one, we have L I seven and then sub three or rather the subscript is three. Yes. And actually just to make a correction for our number of neutrons, we actually would count a total of five spheres which would actually be changing our number of neutrons to five neutrons and making our atomic number calculation be five plus three, which would actually correct to our mass number as being equal to eight. Where in our chemical symbol, we would just make our left hand subscript be the value eight. And so we would have an atomic number of eight, a sorry, a mass number of eight, an atomic number of three. And our chemical symbol being L I for lithium. And so far, we would be able to rule out choices C and D which state that representation one is lithium five. Whereas choices A and B are more correct which state that representation one is lithium eight with three protons. So we would so far be left between choices A and B. Let's move on to representation two where we can count a total of four red spheres corresponding to four protons and we can count a total of four blue spheres corresponding to four neutrons. Now, as we stated before, our number of protons correspond to our atomic number. So our Z value is equal to four and on our periodic table, this will correspond to our atom being beryllium. So we have the chemical symbol B E with a capital B. Next, we want to figure out our mass number A. So we would take our sum of protons being four to our sum of neutrons also being four to get our mass number of eight. Meaning in our chemical symbol, we want a super or on the left hand superscript, the value eight for a mass number. And then in the left hand subscript, you would fill in our atomic number four. So for our representation two, our atomic symbol would be barium eight and choices A and B do both contain that for representation two. So let's move on to representation three where we can count a total of six blue spheres. So that would correspond to six neutrons and three red spheres corresponding to three protons. As we stated before, three protons would correspond to an atomic number expressed by Z equal to three. And on our periodic table, we would find that atomic number three again corresponds to our atom lithium as our chemical symbol where and we need to now figure out our mass number. So taking the sum of our six neutrons plus our three protons, we would find a mass number of nine, meaning our left hand exponent should be the value nine. And then we would fill in our left hand subscript as our atomic number three. And based on choices A and B, it does portray illustration three as lithium nine. So let's move on to illustration four where we can count a total of four red spheres corresponding to four protons. And we can count a total of five blue spheres corresponding to five neutrons. Our number of protons being four tells us our atomic number or Z value is equal to four. And on our periodic table, as we stated before, this corresponds to our chemical symbol for beri calculating our atomic or mass. Sorry, our mass number only and taking the sum between our four protons and our five neutrons, we would have a total of nine as our mass number making our left hand exponent be the value nine. And then our left hand subscript will be our atomic number of four. And so we can also agree with choice A and B which correctly represents our isotope of barium nine for illustration four. And now let's consider the isotopes mentioned in choices A and B in choice A. It states that our isotopes would be representation one and three where in representation one, we had lithium eight and in representation three, we had lithium nine. So we can agree with this because recall that isotopes only have differing mass numbers as we noted, differing A and then in choice A it states that two and four are also isotopes of brillion in which we can see we have brill eight for representation two. And for representation four, we have BRILL nine. So we would also agree with that in choice. A. So A is looking like a good answer. Choice. Let's look at choice B it states that our isotopes are one and two where for one in our in representation one, we determined we have lithium eight and in representation two, we determined we have lithium, sorry in representation two, we have beryllium eight. So we would actually not agree with those being as isotopes because those are completely different chemical symbols we would need, again, just differing mass numbers being our left hand exponent or value A. It also states that representation three which is lithium nine and representation four which is brillion nine are isotopes and we would disagree with that. So choice B we can rule out and this leaves us with choice A which states the correct atomic symbols, lithium eight B eight, lithium nine and brill nine and the correct corresponding isotopes being lithium eight and lithium nine as well as barium eight and barium nine A is our final answer. I hope this made sense and let us know if you have any questions.

For each representation of a nucleus A through E, write the atomic symbol and identify which are isotopes.
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Key Concepts

Atomic Symbol

Isotopes

Nuclear Representation