Molecules And Atoms

Atom and the mechanisms of how particles behave and other materials are proposed for thousands of years.
Especially in the last few centuries, however, these models have been constantly improved and specified.
In the following sections, a cross-section of these developments will be presented, what all the way to our current model of the atom, together with all laws, which are described to control the behavior.

The first model of matter which included elements and atoms was proposed in ancient times.
The Greek philosopher Leucippus (ca. 500-400 B. C. ) And his student Democritus (c. 460-370 B. C.) Were the first to describe the matter in our world as a set of atoms from Greek: indivisible.
Their theory was based on the idea that if any body is divided into its smallest constituent parts, at some point the parts are so small that they can no longer be divided.
You used the word to describe this material yet indivisible.
According to this theory, atoms are small bodies which are not able to be divided.
The atoms of different materials must differ in composition and size.
The characteristics of materials must therefore be determined by differences in their individual atoms: differences in their size, grouping and mutual arrangement.
All beginning of the 19th Century, the Greek model of the atom has been extended and specified by J.
Dalton (1766-1844).
According to his theory, the elements are composed of small particles called atoms that are different, the materials in their mass and size.
During chemical reactions, atoms themselves remain unchanged.
Of course, the number and position of individual atoms in the compound reagent has to change.
They are combined in certain proportions, only to change those combinations and proportions during a reaction.
In the most advanced models of atoms, the atoms and electrons of a core composed.

The atom, of course, is composed of elementary particles.
At the core of an atom are neutrons (no charge) and positively charged protons.
Atoms of the same element always contain the same amount of protons.
Only the number of neutrons can be a little different (in isotopes).
Isotopes are actually different atoms of the same element differing only in the number of neutrons they contain and their atomic weight.
Otherwise, the isotopes of an element usually have the same chemical and physical properties such as    element itself.


The average atomic nucleus is relatively small compared to the atom itself, but it makes up the greatest part of an atom's mass.
The mass of protons and neutrons has been referred to by its number 1.
The number of protons in an atom determines its atomic number.
This number is also used to symbolize    atom or element of the periodic table of elements.
(hydrogen (H)=1, Helium (He)=2), etc.
Electrons negatively charged particles revolve around the nucleus of an atom in electronic orbitals, designated areas where they can be found.
Their mass is relatively small - 1 / 1836 the mass of protons and neutrons.
There is the same amount of electrons as the number of protons in the nucleus.
For this reason, every atom in its natural state, neutral.


Atoms can lose one or more of their electrons.
If they do, they are positively charged.
Or, atoms can gain electrons, which makes them negatively charged.
When an atom loses electrons or gains, it is called an ion.
The outer reaches of an atom, its shell, away from the inner nucleus and where electrons are found, makes up the greatest part of its size.
This area is mostly empty space.
Electrons move in certain designated areas around the atomic nucleus.
Some electrons are closer screened internal orbital, or electron to the nucleus of another.
Others are further away from the nucleus outer orbital electrons.
The nucleus of an atom does not change during a chemical reaction.
For this reason, it does not appear to be very important.
Of course, the electrons of an atom determine its chemical behavior usually these external orbital electrons.


The energy of a specific electron is defined with the help of both letters and numbers, according to the orbital where the electron is found.
Of great importance is the removal of an electron from the nucleus.
The exact placement of an atom's electrons at any one time is impossible to determine, because location and direction of an individual electron are not able to be calculated the Heisenberg Uncertainty Principle.
The more we try to determine the specific position of an electron, is determined the less accurate our ability, the direction.
Why? Because it is impossible to tell which direction that electron will move in the moment we have determined its location.
Unfortunately, only the probability of an electron, where you will be charged.
On the other hand, if we know the direction an electron is moving, its exact location becomes impossible to locate.
The limitation of space, more simply called in which an electron has a certain energy can be found more likely to atomic orbital.


Duality

Because atoms and their electrons cannot be directly investigated, reality at the atomic level is more or less unknown.
From the atomic properties that can be observed, however, the atomic models are made.
The accuracy of these models is seen in their ability to explain certain phenomena.
Often, these extremely small particles have features not customary in the macro world we live in.
Electrons themselves are capable of a certain principle of duality as is light: the duality of waves and particles.
This means that on the one hand, an electron as a particle beam, a bit of act    like a ray gun.
On the other hand, electrons also show a purely wave-like character.
Electrons are not all others, as these are two contradictory characteristics.
Yet we need both concepts to be able to describe an electron's behaviour.
Light wave-like atom model comes from the mechanical description of the outer shell of the atom and the properties of the wave function.


Quantum numbers

In the atomic model of Niels Bohr Danish physicist, an electron cloud swarms around the nucleus of an atom.
The electrons can move only at certain orbital around the nucleus.
The individual orbitals represent a certain amount of energy.
All electrons in an orbital can be seen as the same amount of energy.


The energy of an electron is given by a quantum number n.
The higher the number, the more energy it contains an electron, and so far from the center.


When an electron is excited to a more distant orbital from the nucleus, one with a higher energy, a certain energy must be added to the electron a quantum.
When an electron moves from a higher energy level of orbital to an orbital of low energy, closer to the core, l    energy accounts must be in the form of radiation heat, light, or in the form of a different kind of energy Electromagnetic.
With the help of the main quantum number, we are able to figure the maximum number of electrons in the outer shell of an atom.
The number of electrons an atom can be represented by the formula 2n2, where n is the principal quantum number can be more recent atomic models use other quantum numbers to describe an atom and its electrons.
A secondary quantum number, as I intended, represents the spin of an electron or its angular momentum.
That means its geometric spatial orientation.
This quantity is very important for explaining the disposition of certain chemical bonds in the atoms of a compound.

The energy of a specific electron is defined mainly by the main quantum number n, and to a lesser degree by its secondary quantum number l.
From the position of the energy levels of an electron from its orbit where electron moves, relative to external magnetic field, the magnetic quantum number m also called the quantum number of the direction can be determined.
According to the value of m, orbitals can be divided on the basis of their energy.
C is an s-orbital spherically arranged symmetrically around the center, three p orbitals see the link as three projecting from the core and at their centers and pointed in three directions, five d-orbitals four-sheet structures between p-orbitals and seven f orbitals.
Within the individual types s, p, d, f are individual orbitals of the same energy.
If we take the electron to a small particle, we can imagine that it rotates on its axis, left or right.
The direction of its rotation is termed its spin, and is determined by the quantum number s, for spin.
With the help of these four quantum numbers, each electron can be described accurately.


Stable electron orbitals

The assignment of electrons to their individual orbitals is termed electron configuration.
According to the Pauli principle "Swiss-American physicist" are not more than two electrons in orbit at a particular time.

Orbitals are occupied by electrons from lowest energy orbital to highest energy orbital in the order s, p, d, f.
First, a certain energy of each orbital occupied by one electron.
Then, an orbital of opposite spin moves into an orbital to join the first electron.
Once filled, there are two electrons in an orbital completely.
The two electrons are called an electron pair.
Single electrons are called unpaired electrons.
In each element of the main group, all s and p orbitals are filled gradually, as electrons are added.
For the elements of other groups are the d-orbitals filled.

Ionisation energy

Electrons have a certain amount of energy associated with them, and this energy determines their distance from the nucleus.
If energy is added to an electron, an electron to increase its distance from the nucleus, or even to escape from the nucleus.
In the latter case, an atom becomes a positively charged ion.
The amount of energy needed for an electron to leave called atomic ionization.
Therefore, the ionisation energy necessary to free an electron in an outer orbital from an atom is less than for an electron which is closer to the nucleus.
The density of an element is a number on the way the question about an item, where organized around its atoms, on average.
The density of different elements can only be compared given the same volume.
The density is a function of both mass and volume.


Density units are often given as kg/m3 or g/cm3.
The density of a number of materials are contained in Tables.


At first glance, many elements share a number of characteristics.
A comparison of most of these features, like color, state of matter (solid, liquid, gas), l smell, l  flammability and density so that a substance can be distinguished from a more.
When substances characteristics are compared and contrasted, they can be divided into groups.
The main groups that have to do with chemistry: acids, bases, oxides, salts, metals, hydrocarbons and polymers materials with a large number of atoms that their models are repeated at regular intervals.


Molecules and Moles

The smallest possible chemical unity is formed by the union of a number of atoms - a compound - also called a molecule.


In chemistry, we use the variable "n" very often as a measure of the amount of a certain substance.
We can imagine this amount of a substance as a chemical dozen, an even unit, so to speak.
And just as a dozen or 12, a mole is always a number of particles.
Of course, this number is more than 12, because of the minute size of atoms and molecules.
It would be difficult to count in multiples of 12.


One mole is given as 6.
This seemingly arbitrary amount of particles is actually based on a chemical truth, using carbon chemical symbol C, because this element plays one of, if not the, most important role in chemistry.
Why is the number of smallest particles so important in chemistry? The answer to this question has to do with the nature and types of chemical reactions.
For example, water is actually the combination, or a compound, of two atoms, two atoms of hydrogen and one atom of oxygen.


In the laboratory, a chemist cannot determine the amount of a substance by deduction, or by some type of instinct.
The quotient of a certain amount of mass "m" and an amount of substance "n" is given by the molar mass "M", with the unit number of grams per one mole.
Molar mass is the sum of the mass of individual atoms in a molecule.
Atomic masses are easily attainable, from the periodic table of the elements.
(Hydrogen (H) 1g/mol, helium (He) 4 g / mol, lithium (Li) 7g/mol, beryllium (Be) 9 g / mol, etc..).
See the periodic table of atomic masses for more.

The molar mass of water (H2O) is 18 grams per mole: 1g/mol for each hydrogen atom (H) and 16 g/mol for the one oxygen atom (O).
The amount of particles corresponding to 1 mole of water is 6.
10 23 molecules of water.
The variable masses of individual molecules is a function of the bonding capabilities of those molecules' constituent atoms, and their atomic masses.
If during a chemical reaction a compound, or other products of that reaction have less mass than the original reactant materials, most likely one of the products is not easily detectable - possibly an invisible, odourless gas, or some other byproduct of the reaction.
When scientists compare the exact quantity of reactant materials to the weight of all goods is the same amount is always present on both sides.
Matter is neither created nor destroyed; it can only change form.
A mixture of a solid material is dissolved in a liquid that these mixtures can be measured by their volumes.
Liquid amount of material in the same volume of solution from a dissolved mixture to country, but to determine the amount of a dissolved substance in a solution, we use the chemical formula concentration (symbol: c), a measure of its variable "strength".
Substance concentration is indicated as the concentration of a substance in solution.
We call this amount of solution a one molar solution of carbon, and abbreviate it as 1 M.
The mass of the dissolved substance is calculated from the necessary material mass and mass of one mole of the material.


For example, for a 1 molar solution of table salt we need 58.
5 g salt in 1 liter of water.
Table salt is made of one part sodium and one part chlorine.
The chemical formula of this compound is NaCl.
The mass of one mole of NaCl is 58.
5 g, with sodium (Na) has a molecular weight of 23 g and chlorine (Cl) with an atomic mass 35.
5 g.
5 = 58.
The mass of one mole is easily attainable from the periodic table of the elements.
That is, a 1 molar solution does not guarantee that there is 1 liter of solution.
In our example with table salt, then, rather than use 58.
5 g NaCl in 1 liter of water, d   we could just as easily use 29.
25 g of NaCl with 0.
5 liters of water or 117 g of salt with 2 quarts of water.


Chemical symbols

Substances and chemical reactions can be denoted in a simple and straightforward way in chemistry.
A system of symbols, abbreviations and chemical formulas are used and these are all internationally recognized - thanks to a committee of international experts who agreed these symbols.
At first, however, somewhat abstract symbols were used.
Today's system was introduced by J.
Berzeliem "Swedish chemist 1779-1848".


Elements are made up of small particles of one and only one kind.
In some elements, atoms combine in their natural state, in twos or even more, to form a compound of the given element.
In this case, atoms of one element joined tightly, and hence greater chemical stability.
We call these combinations molecules and molecular substances.
The molecules are often the smallest components gaseous or liquid.
For example, atoms of hydrogen, nitrogen and oxygen are always joined together, in pairs, two each.
There are molecules, but which are of different elements.
The compound " water " is made of one atom of oxygen and two atoms of hydrogen.
In the language of chemical symbols, an element symbol is often combined with these numbers, and is called a chemical formula.
 And, after each element symbol, the number of atoms of that element contained in the compound is given.
Ones, as in one atom of an element, are understood, and therefore not written, as in the chemical formula of water, H2O, understood as two atoms of hydrogen, and one atom of oxygen.


The formula of a compound characterises the material it represents and denotes its constituent elements, the elements it is made of.
At the level of individual particles, the formula represents a molecule and gives the sum of the atoms in the molecule, and their relationship to each other.
The ratio of the number of individual atoms in a molecule can be calculated for example with the help of the mass ratio of the individual elements and their atomic masses.
Stoichiometry says that the atoms in a compound each other in relationships that you invariably.


1. Dalton's Law: The relationship between the masses of the two elements that are bound together in a molecule can be given as the ratio of one integer to another.

2. The law of consistent proportions: Elements combine together in certain specific ratios of masses or in whole number amounts.
The true chemical formula of a number of compounds can be determined rather simply, however, if we know the bonding possibilities of individual elements they are valence.
For example, once we know the bonding possibilities of an element, we can figure out quickly how many hydrogen atoms could conceivably bond to it.
For example: in water "H2O" one oxygen atom "O" bonds with two hydrogen atoms "H" and therefore has a valence of 2.
In the chemical bond, or elements of their atoms are united not only in whole numbers, but their mass ratios also remain constant.
For example, in the chemical reaction of iron "Fe" se sulfur "S" iron sulfide "FeS" is formed.
The relationship between the number of individual atoms is 1:1.
The ratio of masses of the individual atoms is determined from the atomic masses of sulphur and iron, and is 1.