As always, thanks so much for submitting your Stump the Scientist questions! We appreciate everyone playing along with us. Read on to find out the answer to this week’s question!
Question from Facebook fan Zane Shirley-Howell:
How does matter hold itself together? Opposite charges of every atom should push apart.
Response from Chief Scientist Jim Bray:
Atoms are composed of a positively charged center, called the nucleus, surrounded by a cloud of negatively charge electrons. The first thing we should know is that opposite electrical charges attract each other, not repel; it is the same kind of charges that repel. So it is no surprise that the negatively charged electrons are attracted to the nucleus, which is oppositely charged, and the atom holds together.
When we look a little closer, there is a bit of a mystery: the nucleus gets its positive charge from several protons (in all cases but one), all with the electrical charge +1. The nucleus is very compact and occupies a very small amount of space in the atom’s center, and yet it does not come apart from the electrical repulsion of all the positively charged protons within it. The reason is that there is another force in nature within the nucleus called the “strong force”, and it acts at the small distances between all the particles in the nucleus to provide an attraction among them. The strong force is stronger than the electrical repulsion and so holds the nucleus together. So the atoms are stable.
At a larger scale, matter is made of atoms which are joined together chemically. Since the atoms are electrically neutral (having as many positive as negative charges), electrical repulsion is not a significant factor at these higher levels of aggregation.