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Atomic index:



Atomic structure

An atom is composed by the nucleus and the electrons that move around it. In the animation below, the electrons are the red dots moving around the pink nucleus, in elliptical orbits. I have also made an animation where the shells are circular. (remember that none of these models correspond to the true movement of electrons, which is described only by quantum mechanics- nevertheless, these models provide very useful information and understanding).

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Everything we know is formed using the 92 elements in the periodic table, which represent atoms.

What is an atom?

The atom pictured above has 9 electrons (and consequently, 9 protons), what means that it is a fluorine (F) atom.

The distance between the nucleus and the electrons is very large. If the nucleus was a football in the midfield, the electrons would be moving as far as the outer walls of the stadium. Rutherford was the scientist who discovered that, and the consequence is that matter is formed with large empty spaces inside it.

The nucleus is formed by 2 types of particles: protons an neutrons. Both have the same mass, which is approximately a thousand times larger than the mass of the electrons. That is why only the mass of the nucleus is taken into consideration with the purpose of finding the mass of the atom.

Electrons are negatively charged and protons are positively charged (neutrons are neutral). As a result, the atom is held together by electric attraction.

Because matter is neutral, and all atoms must be neutral, the number of electrons and protons must be the same, so that the positive charges are balanced by the negative charges.

If this balance is broken, in the case atoms gain or lose electrons, the atom is called an ion.

In the case of electron gain the ion formed is negative and in the case of electron loss, the aion formed is positive.

Atoms are charcterized by their atomic numbers.

This animation (on this page) is more realistic than the one shown in the electronic shells section, because the orbits here are elliptical and the electrons move faster.

At present it is known that the orbits are not elliptical either. Electrons actually move in orbitals, which are areas where the probability of finding them is higher.


Atom animation with shells (well defined orbits)>>




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