We can represent atoms by listing the number of protons, neutrons...

Question

We can represent atoms by listing the number of protons, neutrons, and electrons—for example, 2p+,2n0,2e− for helium. Which of the following represents the 18O isotope of oxygen?
a. 7p+,2n0,9e−
b. 8p+,10n0,8e−
c. 9p+,9n0,9e−
d. 10p+,8n0,9e-

Accepted Answer

Hello everyone and welcome to today's video stating which of the following represents the N- 15 isotope of nitrogen. So before we jump right into the problem, let's talk about what an isotope is. Now, I want you to recall from Jason's videos the definition of an isotope. Well, an isotope is really any two or more atoms of the same element that differ only in their number of neutrons. So these atoms of the same elements are going to have the same number of protons and electrons. However, in their nucleus, they're going to have a different number of neutrons. Now, this definition is reflected in all of our answer choices from A to D. As we can see all of our answer choices have the same number of protons represented by the letter P plus and in this case it's seven protons all over answer choices also have the same number of electrons represented by e minus, which in this case is also seven. However, when we take a look at the number of neutrons represented by n zero, we can see that it ranges from 7 to 10. So each answer choice has a different number of neutrons. Now let's go ahead and try to solve this problem. Whenever we're given the name of an isotope such as N- 15 this term and 15 represents the mass number of that isotope. So now I want you to recall the formula for the mass number since this is what it's going to allow us to determine the specific number of protons neutrons and electrons in that specific isotope. Well, the formula for the mass number of any isotope equals the number of protons in the isotope represented by P plus plus the number of neutrons in the isotope. So it only takes into account the number of protons and neutrons in the nucleus of the isotope to determine the mass number. As we can see all over answer choices Has seven protons in their nucleus. So we're going to be using that as a number of protons. The isotope in question is labeled and 15. So the mass number of the isotope is 15. And the only thing that we do not know since it's variable in our answer choices is the number of neutrons. So we're going to assign a variable to that value. In this case the variable is going to be X. Now, if we distribute this equation and solve for X, we're going to find that X equals 15 minus seven. If we perform this calculation, we're going to find that X equals eight. Now X recall that it's the number of neutrons in the isotope. Now we have been able to determine that the number of neutrons in the isotope is eight. The only answer choice that has a new trans is answer choice B. All the answer choices as a different number of nutrients and do not correlate with this ice a tool. So we're going to highlight answer choice B as our final answer. Thank you very much for sticking around until the end of this video. I really hope it helped you.

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