I propose a summary of the material using the atomic theory of Prof. Arrigo Amadori
--- 01 - atom.
matter consists of atoms. An atom consists of a core positively electrically charged and a number of electrons, negatively charged, which revolve around.
The core is composed of protons, which are positively charged particles and neutrons particles that are free of charge.
The mass of a proton is approximately equal to the mass of a neutron and both are about 2000 times heavier than an electron. 'S why which are the electrons that revolve around the nucleus (much heavier) and not vice versa. The nucleus is very heavy and "concentrate" while the electrons are very light and mobile.
Normally, the number of electrons that orbit the nucleus equals the number of protons that make up the nucleus. Since that amount of equal value (apart from the sign), an atom is normally electrically neutral . For this reason (and thankfully, otherwise the bodies would be thrown in all directions, since the electric force rather strong) the material is normally electrically neutral.
matter, even if it is thick and "hard", is in fact almost empty. If, by the aspect ratio, consider the size of an apple core, electrons revolve around a distance of approximately one kilometer. This is of extreme importance and, if somehow we could eliminate all this space, we can "shrink" all the mass in a very small space raggiungendodensità enormous. This is what happens to blacks in the holes and neutron stars in which, for example, all the huge mass of a star is compacted into a space of a few cubic miles.
An atom is then composed of a nucleus consisting of nucleons (protons and neutrons) and electrons (in egualnumero protons, when the atom is electrically neutral) that revolve around it. Each atom is indicated by a symbol and two numbers: the atomic number (the number of protons is identical to the number of electrons) and the mass number (the number of nucleons, ie protons and neutrons that make up the nucleus).
The number of neutrons is given, of course, the mass number - atomic number.
Example (helium atom):
An atom can exist in nature with the same number but different atomic mass number. Such atoms are called isotopes and have the same chemical properties (ie, to create compounds, molecules, the same property). An example for this is the hydrogen atom . In nature it is present in the vast majority consists of a proton and an electron that revolves around it. There is, however, in smaller quantities, even the deuterium, which consists of one proton, one neutron and one electron. With it forms heavy water. There is also the tritium (rarer) consists of a proton, two neutrons and an electron. Chemically, hydrogen, deuterium and tritium have the same property (because they have the same number of protons and electrons). In summary:
atoms exist a nature are about 90 listed in a table called the periodic table of elements or table of Mendeleyev:
http://www.apsidium.com/ext_pt/expertab.htm
02 - Chemical bonds
atoms to the left of this table are those metals and have the property of losing electrons to become ions positive. Atoms in the right places, however, are not those metals and have the ability to acquire electrons, ie to become negative ions . The other properties of atoms lose electrons
or buy a less clear-cut. Some atoms may even behave like metals or non-metals as appropriate.
attitude which atoms acquire or lose electrons causes the formation electrical connections between them and that's how molecules are formed , the fundamental constituents of chemical compounds that make up matter.
The simplest type of bond established between the atoms is called ionic bond . It 's the case of table salt, sodium chloride, NaCl. In it, the sodium becomes a positive ion and a chlorine negative ion.
These ions attract each other electrically, and form a regular lattice:
Other types of chemical bonds are based on the fact that electrons are shared by the atoms forming the bond. This is the covalent bond.
It 's very interesting case of' water :
The electrons are shared oxygen atom and two hydrogen atoms so asymmetric.
The electrons from the tents to be more oxygen and therefore the water molecule acts as a electric dipole, or an object with electrical polarity. If
dive, for example, the salt water, the water dipoles break up the lattice of the salt ions inserted between the Na and Cl by ensuring that the salt you melt (while maintaining the link between sodium and chlorine).
If we insert two electrodes in the solution connected to a battery, is the phenomenon of ' electrolysis : ions dissolved in water tend to go, breaking the bonds, to the electrodes with opposite sign.
sodium ions, positive, tend to go towards the negative electrode, the cathode, and chlorine ions, negatives, make to move toward the positive electrode, the anode. This will break the chemical bonds between sodium and chlorine and the electrodes are deposited these atoms (at least theoretically, because in reality things are increasingly complicated, so, in effect, the cathode comprises hydrogen!).
03 - The states of matter.
The matter is in various states ..
If electrical connections between the molecules are strong , the material is presented to the state solid and the molecules are arranged to form a lattice (which may be regular or irregular (amorphous)). The molecules fluctuate around points so fixed geometry without departing significantly from them.
If the electrical connections between the molecules are weaker , it has the liquid. In this state, the bonds are weaker than the solid state, but strong enough to force the liquid (due to gravity) in a container. In this case you do not have a lattice and the molecules have the ability to translate disorderly without abandoning the liquid (if not sporadically (evaporation)).
If the electrical connections between molecules are weak or almost absent, it has the gas. The molecules are free to move and go anywhere in the available space.
04 - atomic models.
In this section we briefly describe the most important atomic models that historically have been proposed. The hypothesis
that matter is composed of atoms goes back to Democritus (400 BC). Atom in greek
means "not divisible." The idea, however, was opposed by atomistic Aristotle, which later became the philosopher "official" church. For this reason we have to wait until as late as 1800 because scientists reconsider the atomic hypothesis. In 1803
Dalton explained the well-known chemical phenomena by which substances are formed from their components according to well-defined relations between integers, assuming that matter was made up of atoms
.
With the discovery of natural radioactivity , it became later that atoms were indivisible particles, they were composed of smaller parts. In 1898
Thomson proposed the first physical model of the atom. He imagined an atom
was made up of a small sphere of positively charged matter (protons and neutrons
had not yet been discovered) in which negative electrons (recently discovered) were immersed.
Rutherford In 1911 he made a crucial experiment to test the model of Thomson.
bombards a thin sheet of gold with alpha rays (helium atoms fully ionized, this private
of electrons). The experiment led to the finding that alpha rays were almost never deviated. They crossed the piece of gold without hardly be disturbed. Only some alpha rays (1%) were diverted from the Gold Leaf and were remarkably (some even were completely rejected).
Based on this fundamental experiment, Rutherford proposed a model of the atom
in which nearly all the mass of the atom is concentrated in a very small portion, called
nucleus (positively charged) and electrons revolve around him as well as
planets revolve around the sun.
The core is so concentrated that the electrons revolve around the distance its huge.
Rutherford's model does have a great "defect" that causes a crisis. According to electromagnetic theory an accelerated charge in motion (not in uniform rectilinear motion)
emits electromagnetic waves and therefore loses energy. For this reason, the electrons of the atom
Rutherford, why rotate on circular orbits, should radiate electromagnetic
and then, losing energy, fall in the nucleus but not
thing that happens because the atoms are very stable objects ( matter appears normally stable). In 1913
Bohr proposed an amendment to the conceptual model of Rutherford. While agreeing
the idea of \u200b\u200b"planetary model", postulates that the electrons were available orbits of "parking" fixed in which they do not emit or absorb energy. An electron emits or absorbs electromagnetic energy in the form of electromagnetic waves only if jumps from one orbit to another .
This idea is not compatible with the laws of classical physics (Newton), is based on the ideas of the emerging quantum mechanics .
The Bohr model explains very well the hydrogen atom but not more complex ones. Sommerfeld then proposed a correction to the Bohr model according to which there was a good match between theory and observations spectra of atoms (a spectrum is the set of frequencies of electromagnetic radiation emitted or absorbed by the electrons of an atom).
Next, we came to an atomic model more consistent with the great progress that
quantum mechanics in the meantime he had done.
In 1930 it was discovered the neutron for which you came soon to a model of almost complete
in which the center is the nucleus composed of protons (positive) and neutrons (protons and neutrons are collectively called nucleons) and revolve around the electrons. The idea of \u200b\u200b
as the electrons orbit the nucleus was deeply amended in the light of the discoveries of quantum mechanics.
was abandoned the notion of orbit and was introduced to the concept of orbital .
According to quantum mechanics an electron not be described in terms of trajectory .
can not therefore say with certainty where an electron is in a certain time or where you will find
in a moment later. You can only know the probability
of finding the electron in a certain point in space.
An orbital is a trajectory in which an electron (according to the ideas of classical physics) can be
, is instead a "cloud " probability where you can find the electron.
Examples of orbitals for the hydrogen atom where more light means more chances of finding the electron (in section):
--- 01 - atom.
matter consists of atoms. An atom consists of a core positively electrically charged and a number of electrons, negatively charged, which revolve around.
The core is composed of protons, which are positively charged particles and neutrons particles that are free of charge.
The mass of a proton is approximately equal to the mass of a neutron and both are about 2000 times heavier than an electron. 'S why which are the electrons that revolve around the nucleus (much heavier) and not vice versa. The nucleus is very heavy and "concentrate" while the electrons are very light and mobile.
Normally, the number of electrons that orbit the nucleus equals the number of protons that make up the nucleus. Since that amount of equal value (apart from the sign), an atom is normally electrically neutral . For this reason (and thankfully, otherwise the bodies would be thrown in all directions, since the electric force rather strong) the material is normally electrically neutral.
matter, even if it is thick and "hard", is in fact almost empty. If, by the aspect ratio, consider the size of an apple core, electrons revolve around a distance of approximately one kilometer. This is of extreme importance and, if somehow we could eliminate all this space, we can "shrink" all the mass in a very small space raggiungendodensità enormous. This is what happens to blacks in the holes and neutron stars in which, for example, all the huge mass of a star is compacted into a space of a few cubic miles.
An atom is then composed of a nucleus consisting of nucleons (protons and neutrons) and electrons (in egualnumero protons, when the atom is electrically neutral) that revolve around it. Each atom is indicated by a symbol and two numbers: the atomic number (the number of protons is identical to the number of electrons) and the mass number (the number of nucleons, ie protons and neutrons that make up the nucleus).
The number of neutrons is given, of course, the mass number - atomic number.
Example (helium atom):
An atom can exist in nature with the same number but different atomic mass number. Such atoms are called isotopes and have the same chemical properties (ie, to create compounds, molecules, the same property). An example for this is the hydrogen atom . In nature it is present in the vast majority consists of a proton and an electron that revolves around it. There is, however, in smaller quantities, even the deuterium, which consists of one proton, one neutron and one electron. With it forms heavy water. There is also the tritium (rarer) consists of a proton, two neutrons and an electron. Chemically, hydrogen, deuterium and tritium have the same property (because they have the same number of protons and electrons). In summary:
atoms exist a nature are about 90 listed in a table called the periodic table of elements or table of Mendeleyev:
http://www.apsidium.com/ext_pt/expertab.htm
02 - Chemical bonds
atoms to the left of this table are those metals and have the property of losing electrons to become ions positive. Atoms in the right places, however, are not those metals and have the ability to acquire electrons, ie to become negative ions . The other properties of atoms lose electrons
or buy a less clear-cut. Some atoms may even behave like metals or non-metals as appropriate.
attitude which atoms acquire or lose electrons causes the formation electrical connections between them and that's how molecules are formed , the fundamental constituents of chemical compounds that make up matter.
The simplest type of bond established between the atoms is called ionic bond . It 's the case of table salt, sodium chloride, NaCl. In it, the sodium becomes a positive ion and a chlorine negative ion.
These ions attract each other electrically, and form a regular lattice:
Other types of chemical bonds are based on the fact that electrons are shared by the atoms forming the bond. This is the covalent bond.
It 's very interesting case of' water :
The electrons are shared oxygen atom and two hydrogen atoms so asymmetric.
The electrons from the tents to be more oxygen and therefore the water molecule acts as a electric dipole, or an object with electrical polarity. If
dive, for example, the salt water, the water dipoles break up the lattice of the salt ions inserted between the Na and Cl by ensuring that the salt you melt (while maintaining the link between sodium and chlorine).
If we insert two electrodes in the solution connected to a battery, is the phenomenon of ' electrolysis : ions dissolved in water tend to go, breaking the bonds, to the electrodes with opposite sign.
sodium ions, positive, tend to go towards the negative electrode, the cathode, and chlorine ions, negatives, make to move toward the positive electrode, the anode. This will break the chemical bonds between sodium and chlorine and the electrodes are deposited these atoms (at least theoretically, because in reality things are increasingly complicated, so, in effect, the cathode comprises hydrogen!).
03 - The states of matter.
The matter is in various states ..
If electrical connections between the molecules are strong , the material is presented to the state solid and the molecules are arranged to form a lattice (which may be regular or irregular (amorphous)). The molecules fluctuate around points so fixed geometry without departing significantly from them.
If the electrical connections between the molecules are weaker , it has the liquid. In this state, the bonds are weaker than the solid state, but strong enough to force the liquid (due to gravity) in a container. In this case you do not have a lattice and the molecules have the ability to translate disorderly without abandoning the liquid (if not sporadically (evaporation)).
If the electrical connections between molecules are weak or almost absent, it has the gas. The molecules are free to move and go anywhere in the available space.
04 - atomic models.
In this section we briefly describe the most important atomic models that historically have been proposed. The hypothesis
that matter is composed of atoms goes back to Democritus (400 BC). Atom in greek
means "not divisible." The idea, however, was opposed by atomistic Aristotle, which later became the philosopher "official" church. For this reason we have to wait until as late as 1800 because scientists reconsider the atomic hypothesis. In 1803
Dalton explained the well-known chemical phenomena by which substances are formed from their components according to well-defined relations between integers, assuming that matter was made up of atoms
.
With the discovery of natural radioactivity , it became later that atoms were indivisible particles, they were composed of smaller parts. In 1898
Thomson proposed the first physical model of the atom. He imagined an atom
was made up of a small sphere of positively charged matter (protons and neutrons
had not yet been discovered) in which negative electrons (recently discovered) were immersed.
Rutherford In 1911 he made a crucial experiment to test the model of Thomson.
bombards a thin sheet of gold with alpha rays (helium atoms fully ionized, this private
of electrons). The experiment led to the finding that alpha rays were almost never deviated. They crossed the piece of gold without hardly be disturbed. Only some alpha rays (1%) were diverted from the Gold Leaf and were remarkably (some even were completely rejected).
Based on this fundamental experiment, Rutherford proposed a model of the atom
in which nearly all the mass of the atom is concentrated in a very small portion, called
nucleus (positively charged) and electrons revolve around him as well as
planets revolve around the sun.
The core is so concentrated that the electrons revolve around the distance its huge.
Rutherford's model does have a great "defect" that causes a crisis. According to electromagnetic theory an accelerated charge in motion (not in uniform rectilinear motion)
emits electromagnetic waves and therefore loses energy. For this reason, the electrons of the atom
Rutherford, why rotate on circular orbits, should radiate electromagnetic
and then, losing energy, fall in the nucleus but not
thing that happens because the atoms are very stable objects ( matter appears normally stable). In 1913
Bohr proposed an amendment to the conceptual model of Rutherford. While agreeing
the idea of \u200b\u200b"planetary model", postulates that the electrons were available orbits of "parking" fixed in which they do not emit or absorb energy. An electron emits or absorbs electromagnetic energy in the form of electromagnetic waves only if jumps from one orbit to another .
This idea is not compatible with the laws of classical physics (Newton), is based on the ideas of the emerging quantum mechanics .
The Bohr model explains very well the hydrogen atom but not more complex ones. Sommerfeld then proposed a correction to the Bohr model according to which there was a good match between theory and observations spectra of atoms (a spectrum is the set of frequencies of electromagnetic radiation emitted or absorbed by the electrons of an atom).
Next, we came to an atomic model more consistent with the great progress that
quantum mechanics in the meantime he had done.
In 1930 it was discovered the neutron for which you came soon to a model of almost complete
in which the center is the nucleus composed of protons (positive) and neutrons (protons and neutrons are collectively called nucleons) and revolve around the electrons. The idea of \u200b\u200b
as the electrons orbit the nucleus was deeply amended in the light of the discoveries of quantum mechanics.
was abandoned the notion of orbit and was introduced to the concept of orbital .
According to quantum mechanics an electron not be described in terms of trajectory .
can not therefore say with certainty where an electron is in a certain time or where you will find
in a moment later. You can only know the probability
of finding the electron in a certain point in space.
An orbital is a trajectory in which an electron (according to the ideas of classical physics) can be
, is instead a "cloud " probability where you can find the electron.
Examples of orbitals for the hydrogen atom where more light means more chances of finding the electron (in section):
