Scienze e Viaggi

The atoms and the molecules in our days

At the beginning of the '900 have been uncovered that the matter and the electric charges exist like particles still more small than an atom: the protons, the electrons and the neutrons. But atom theory comes from afar........

The proton is the particle that it has positive electrical charge with unitary value and one unitary mass equivalent to that one of hydrogen, smallest of atoms.

Therefore the proton has charge + 1 and mass 1.

The electron is a particle that it has equal charge but negative, that is - 1, and a negligible mass because it is 1837 times smaller of the proton.

The neutron is the sum of a proton and an electron.

At first it was proposed an atom model like a little ball, then similar to a solar system in miniature.

1. At the centre of the atom there is the nucleus, constituted from some protons and some neutrons, leant against one to the others. The nucleus has positive electrical charge and concentrates nearly all the mass of the atom.
2. Round the nucleus the electrons rotate. Their number is equivalent to that one of protons, therefore the atom is electrically neutral.

With the discovery of subatomic particles and with the new atomic model it has been completed an other great unification of the nature. All the atoms of the various elements are, in fact, referable to three essential constituents: the protons, the electrons and the neutrons. The atoms only differ for the number of present protons in the nucleus. This is the atomic number, and varies from 1 to 103 like the series of integers.

The molecules are formed because the atoms tend to exchange electrons.

For example the kitchen salt is constituted from many little cubes more or less regular. Even if we crush a piece of big salt, we obtain fragments that have always flat and perpendicular faces between them, like those of a cube. The solid substances that are made up forming pieces with flat and regular faces come calls crystals. The regular shape of crystals is one consequence of the atomic structure of the matter.

In this molecule a sodium atom (Na) misses an electron and takes on positively. At the same time a chlorine atom (Cl) acquires this an electron takes on negatively. Consequently the chlorine atom and sodium atom attract them and form a compound NaCl that is the chloride of sodium, known like kitchen salt.

The chemistry studies like the atoms exchange electrons to form molecules and how the electrons are inside the molecules.

Now the scientists discover that other sub - atomic particles can exist inside the atom: for examples the quarks.

We are interesting to two kinds of quarks: up-quark and down-quark.

Two up-quark + 1 down-quark form a proton, instead 1 up-quark + 2 down-quark form a neutron, with this rule we built the atoms from hydrogen to carbon, also you can do if you go to this site: http://www.pbs.org/wgbh/aso/tryit/atom/.

the parade of atoms