atom consists of two main parts: the nucleus and the electron shell.In turn, the core is the combination of protons and neutrons, which together are called nucleons;electron shell of the nucleus consists of only electrons.The nucleus has a positive charge, the shell - negative, and together they form an electrically neutral atom.
As mentioned earlier, the atom consists of a nucleus and electrons moving around it.Often, to simplify the schematic drawings atoms, believe that the electrons move in circular orbits, the planets of the Solar System around the sun.This visual model proposed in 1911 by the celebrated British physicist Ernest Rutherford.However, experimentally to prove it was not possible, and the term
"orbit" began to be phased out.Already in the early 30s of the twentieth century, it was finally established that the electron in an atom has no definite trajectory.That's when the American physicists Robert Mulliken and German physicist Max Born began to emerge a new term - orbital - in tune and close within the meaning of the orbit.
electron cloud - it is the whole set of points at which the electron has visited over a certain period of time.That area of the electron cloud in which electrons appear more often, and have orbital.Most often, giving definition to the term, say that it is the place of the atom, where electrons are most likely location.Thus the word "probably" plays a key role.In principle, an electron can be in any part of the atom, but the probability of finding it anywhere outside the orbital extremely small, so it is assumed that the orbital is about 90% of the electron cloud.Graphically depicted as the orbital surface, which outlines the area where the electron is most likely occurrence.For example, a hydrogen atom orbital is spherical.
Currently, scientists determine the five types of orbitals: s, p, d, f and g.Their shapes were calculated by quantum chemistry methods.Orbitals exist regardless of whether the electrons on them or not, wherein the atoms of each element, known now has a complete set of orbitals.
In modern chemistry orbital is one of the key concepts, which allows you to explore the processes of formation of chemical bonds.