Bohr's model can be used for hydrogen-like ions—ions that have only one electron, such as He⁺ and Li²⁺. (a) Why is the Bohr model applicable to He⁺ ions but not to neutral He atoms?

Video transcript

Hey everyone in this example, we need to determine which of the below statements is a true statement. At a glance for all of our answer choices. They're all in regards to the Bohr model and we should recall that the Bohr model is used for hydrogen like atoms or rather ions we should say. And in this case, what hydrogen like means is having at least one electron. So looking at statement A it says that the Bohr model is applicable to helium because it is a hydrogen like ion, we would recognize helium on our periodic table with the atomic number two. So we would recall that atomic number can be represented by the symbol Z. So we would say that Z equals two and so therefore we have two electrons in helium. So we would rule out choice A because it's not applicable to the Bohr model, it's not like helium or hydrogen. Sorry. So moving on to statement B, it says that the Bohr model is applicable to lithium because it's a hydrogen like ion. When we think of lithium on the periodic table, we would find it in group one A. And we would see that it has the atomic number or Z value equal to three, which would correspond to three electrons for the neutral atom lithium. And so because it does not have one electron like hydrogen, we would also rule out statement B because it's not a true statement, it's a false statement just like statement A. So moving on to statement see it says that the Bohr model is applicable to the lithium two plus carry on because it is a hydrogen like ion, we should recall that having a carry on charge means we lose that number of electrons. So because we have a two plus charge on this carry on from our three electrons in a neutral atom of lithium we would lose to. And so that would leave us with one electron, which is equivalent to the one electron in a hydrogen atom. And so because this is or this matches up with the one electron in a hydrogen atom. This would be a true statement. And so we can consider choice. See a good anti choice. Moving onto choice D. We have the Bohr model is only applicable to the hydrogen atom. We know that this is not true because it's applicable to any ion that is hydrogen like meaning it will have one electron. And so that means that choice C is the only true statement. So it's our final answer for this example. If you have any questions, please leave them down below. Otherwise, I will see everyone in the next practice video