the greater is its charge, and, in turn, the more electrons can be
held like satellites around it, to make an atom in which the positive
and negative charges counter-balance, leaving the atom overall
neutral. Thus it is that although intense electrical forces are at
work deep within the atoms of our body, we are not much aware of
them, nor are we ourselves electrically charged. The atom of the
simplest element, hydrogen, consists of a single proton and a single
electron. The number of protons in the nucleus is what
differentiates one element from another. A cluster of 6 protons
forms the nucleus of the carbon atom, iron has 26, and
uranium 92.
Opposite charges attract, but like charges repel. So it is a wonder
that protons, which are mutually repelling one another by this
electrical force, manage to stay together in the confines of the
nucleus. The reason is that when two protons touch, they grip one
another tightly by what is known as the strong force. This attractive
force is much more powerful than the electrical repulsion, and so it
is that the nuclei of our atoms do not spontaneously explode.
However, you cannot put too many protons in close quarters;
eventually the electrical disruption is too much. This is one reason
why there is a heaviest naturally occurring element, uranium, with
92 protons in each nucleus. Pack more protons than this together
and the nucleus cannot survive. Beyond uranium are highly
radioactive elements such as plutonium whose instability is
infamous.
Atomic nuclei of all elements beyond hydrogen contain protons
and also neutrons. The neutron is in effect an electrically neutral
version of the proton. It has the same size and, to within a fraction
of a percentage, the same mass as a proton. Neutrons grip one
another with the same strength that protons do. Having no
electrical charge, they feel no electrical disruption, unlike protons.
As a result, neutrons add to the mass of a nucleus, and to the
overall strong attractive force, and thereby help to stabilize the
nucleus.
4
Particle Physics