What Is the Center of an Atom Called? Inside the Atomic Nucleus
The center of an atom is called the nucleus. It is a small, dense region containing protons and, in most atoms, neutrons. Nearly all of an atom’s mass is concentrated in its nucleus, while electrons occupy the space around it.
The nucleus is much smaller than the atom as a whole. An atom’s size is set mainly by the region occupied by its electrons, not by the nucleus. This is why atoms are often described as mostly empty space, though electrons are better understood as occupying regions of space than as tiny particles moving along fixed paths.
What is in the nucleus?
Protons have a positive electric charge. Neutrons have no electric charge. The number of protons in a nucleus is the element’s atomic number. If that number changes, the atom belongs to a different element. Atoms of the same element can have different numbers of neutrons; these forms are called isotopes NIST.
Protons repel one another because they carry the same positive charge. The strong nuclear force binds protons and neutrons at very short distances, helping hold the nucleus together Encyclopaedia Britannica.
One example: carbon isotopes
Every carbon nucleus has six protons, because carbon’s atomic number is 6. Carbon-12 has six neutrons as well: its mass number, 12, is the total number of protons and neutrons. Carbon-14 also has six protons, but it has eight neutrons. The two are isotopes of carbon because they have the same number of protons and different numbers of neutrons.
The number after an isotope’s name gives its mass number. Subtract the atomic number to find the number of neutrons.
Key Takeaways
- The center of an atom is its nucleus.
- The nucleus contains protons and, in most atoms, neutrons.
- The number of protons determines which element the atom is.
- Different neutron counts produce different isotopes of the same element.
- The strong nuclear force binds particles in the nucleus at very short distances.
