Opposite charges attract each other via the electromagnetic force. Which of the following pairs of subatomic particles attract each other in this way? protons and protons, electrons and electrons, protons and neutrons, protons and electrons, or electrons and neutrons.
In this question, we’re being asked what we know about subatomic particles. These are the particles which make up atoms. So let’s start by reviewing what we already know about subatomic particles. We can imagine atomic structure to be a bit like this diagram. In the center, we have the nucleus, which is made up of protons and neutrons. Then, around the outside, we have electrons. And we often describe these as existing in shells around the nucleus.
Now we need to consider what we know about each type of subatomic particle. Let’s start with the charge on each one. A neutron is easy to remember if you think of the word neutral. A neutron has no charge at all. A proton has a positive charge. You can remember this because proton and positive both begin with a p. So we can label a proton as having a plus one charge. The electrons therefore are the opposite and are considered to have a negative one charge. This means that we can balance our protons and our electrons to make the atom overall neutral. If the number of protons and electrons is not balanced, we end up with an ion.
Interestingly, protons and neutrons have the same relative mass. So we’ll call this a mass of one. Electrons, however, are very different. If a proton has a mass of one and a neutron has a mass of one, an electron has a mass of one over 1836. What this really means is that electrons are really, really small in comparison to protons and neutrons. But let’s look back at the question and use this information to find the right answer.
We’re told that opposite charges attract each other. And we’re asked which of the following pairs of subatomic particles will attract each other. This means we’re looking for a pair of subatomic particles which have the opposite charges. In answer a, we have protons and protons, both of which are positive. These are not opposite charges and don’t attract each other. In fact, they repel each other. So this is not the correct answer.
For electrons and electrons, we have the same situation. Both have negative charges so do not attract each other. So we can rule this out as well. In c, the protons have a positive charge but the neutrons have no charge. So these aren’t opposite charges. So they don’t attract each other. This rules out c.
Next, we have protons and electrons. As we can see from our table, protons are positively charged and electrons are negatively charged. So these two subatomic particles have opposite charges and will attract each other. So this answer is correct. But we’ll check the last one just to be safe.
The last answer has electrons and neutrons. Electrons have a negative charge, while neutrons have no charge. These are not opposite charges and therefore don’t attract each other. So we’ve ruled out the last answer. So the correct answer to this question, of which pair of subatomic particles attract each other by having opposite charges, is d, protons and electrons.