generalfusion

Electrons, Protons, and Neutrons

The primary building blocks of all atoms are protons, electrons and neutrons.

Protons are positively charged particles that reside in the centre, or nucleus, of an atom. The number of protons in the nucleus defines the type of element and is referred to as its atomic number. For example, hydrogen atoms have one proton each and carbon atoms have six protons each.

Electrons are negatively charged particles that form a complex cloud around the nucleus. Generally, the number of electrons matches the number of protons, so the net charge on an atom is zero, although atoms sometimes lose or gain electrons resulting in a negative or positive charge. Charged atoms are known as ions.

Neutrons are neutral (uncharged) particles that reside in the nucleus of an atom along with the protons.

Atomic forces

The protons and neutrons in the nucleus of an atom are subjected to two fundamental forces. Firstly, an electrostatic force serves to repel the protons from each other since they are of identical charge. This force increases as the number of protons in a nucleus increases since all protons interact with each other. Secondly, the “nuclear force” binds protons and neutrons to their immediate neighbours, overcoming the electrostatic force but only at very short range. The effect of this force increases to a point as more protons or neutrons

are added to a nucleus, forcing them to surround each other. It is for this reason that large nuclei contain proportionally more neutrons than light elements: the extra neutrons stabilize heavy elements because they add the nuclear binding force without adding proton-proton repulsion. The net result of these opposing forces is that the energy that binds together protons and neutrons generally increases with increasing nucleus size, up to the elements iron and nickel, and then decreases for heavier nuclei, which become increasingly unstable.

Isotopes

Each atom has a normal number of neutrons associated with it, although variations in the number of neutrons exist. These variations are known as isotopes. For example, carbon has 6 protons and normally has 6 neutrons (designated as 12C), but also exists as isotopes with 5, 7, 8 or 9 neutrons (11C, 13C, 14C and 15C).

Not all isotopes are stable. For the carbon isotopes mentioned above, 12C and 13C are stable, while 11C, 14C and 15C are unstable. Unstable isotopes decay radioactively to more stable atomic forms and lose sub-atomic particles in the process. This is a random process on the atomic level, but the overall decay of a large number of atoms is characterized by its half-life, which is a measure of how much time passes for half of the original quantity of the isotope to decay to its more stable form. The half-life of 15C and 11C are seconds and minutes respectively, whereas the half-life of 14C is 5,730 years.

Sub-atomic emissions

Sub-atomic emissions take the form of electromagnetic waves or particles, which can include protons and neutrons. When a radioactive emission includes a proton, the resulting atom changes from one element to another. When a radioactive emission includes a neutron, the resulting atom has lower weight and may or may not be stable.

Sub-atomic emissions occur with very high energy (in the form of electromagnetic radiation and particle velocity) due to the strength of the forces involved. By allowing the emitted particles to bombard other elements, their velocity can be converted into heat, which we can transform into other forms of energy to do useful work.

Einstein showed that the mass of a body is a measure of its energy content as expressed by his famous equation, E=mc2 (where E is energy, m is mass and c2 is the speed of light times itself, which is a very large number). The trade-off between mass and energy is imperceptibly small during our normal daily uses of energy, but the energy released by sub-atomic emissions is so great relative to the mass of the original atoms that the effect is both significant and measureable – the mass of the atomic elements left behind after the emissions have occurred is less than the mass of the original constituents.