Video Transcript
The picture shows an electron that
is near to an atomic nucleus. Do the atomic nucleus and the
electron attract or repel one another?
In our picture, we have two
objects: an atomic nucleus and an electron. Our question is asking whether the
nucleus and electron attract or repel one another. This implies that there’s some
force between them. These two objects will have a force
between them if they both have an electric charge. Indeed, that’s the case. An electron has a negative electric
charge, while an atomic nucleus overall has a positive electric charge. Since both objects are charged,
there will be a force between them. What’s more, we know that these
objects have opposite electric charges. Whenever two objects have opposite
electric charges, they attract one another. There will be a force on the
nucleus toward the electron and a force on the electron toward the nucleus. In answer to this question then, we
write that the nucleus and the electron attract each other.
Let’s look now at part two of this
example.
Which of the following statements
is true? (A) The electron can be moved
farther away from the nucleus without doing any work. (B) In order to move the electron
farther away from the nucleus, work must be done on the electron.
We’ve seen from the first part of
this question that there’s an attractive force between the nucleus and the
electron. This force will tend to make the
electron and nucleus move closer together. In this part of our question,
though, we’re imagining moving the electron farther away from the nucleus. To do that, we would need to exert
some force that would overcome this attractive force, drawing the electron and
nucleus together. So we need to exert a force on the
electron, and this force is what would cause it to move farther away. Since we’re exerting a force on the
electron over some distance, that means we’re doing work on it. If we didn’t do any work on the
electron, there’s no way it could move farther from the nucleus. And so we choose answer option
(B). In order to move the electron
farther away from the nucleus, work must be done on the electron.
