What is it?
Quantum means the smallest change is a discrete change rather than a continous band. With an element, the smallest
amount you can have is one atom, the next smallest amount is 2 atoms, etc. - so the quantum, or step, is 1 atom. In relation to the electrons around the nucleus of an
atom, quantum theory says that the lowest energy an electron can have is not zero but something higher. This means that an electron can’t just dive down and sit with
the protons of the nucleus in what is known as the ground state, it must have an orbit and have a specific amount of energy. In the innermost shell of electrons, quantum theory says there can be a
maximum of so many electrons (depending upon the element), and the next electron must have a higher energy and go in the next higher orbit, and so on.
Quantum theory applies to pretty much everything at these small scales (known as the quantum level). An electron has a
discrete charge, so all charge is a multiple of this basic charge. An electron also has a spin and this can only be either one way or the other. All other spin states are
‘prohibited’ - it can’t have no spin, a half spin or a double spin.
When we talk about the outermost valence shell of electrons, quantum theory of course says there can only be so many
electrons in it. However, when an atom has no net charge - it is neutral - and its valence shell is completely full, then it wants to be an insulator and is inert. Its
outermost electrons are ‘happy’ within a fully occupied electron shell with no space for an extra one and the energy to get one out is high. Whether the valence shell is
full or one ‘short’ or only contains one electron - depends upon the element and the chemical & electrical properties change. That is why the periodic table is
periodic. Elements that have an electron short of the happy complement readily accept another electron and then have a net charge of one electron (negative)
Similarly if there is only one electron in the valence shell it can fairly easily lose it and become positively charged (there is then one too few electrons to balance the
number of protons in the nucleus.
There’s lots more REALLY exciting stuff about quantum theory, but too little space here to give it justice. Superconductivity
is a quantum effect and there is a real possibility in the nearish future of being able to build quantum computers that could in theory hold all possible states of a problem at the same time and then collapse the probabilities down to reveal
the single answer (Like an infinitely parallel computer rather than the serial step by step computers we mostly have now).
|
