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The substances are characterized by their name and their physical and chemical properties. However, there are several names misused, confused or rare.
Examples:
oil of vitriol (sulfuric acid)
blue vitriol (copper sulphate)
quicklime (calcium oxide)
off Cal (calcium hydroxide)
If we were to give a complete list of the properties of such substances as melting point, boiling point, color, shape, etc., would be an endless list that hardly anyone can hold in memory, it is easier to name the substance and thus associate its properties.
best in the eyes of a chemical is, the formula. A formula as a symbol, representing a large amount of information quantitative and qualitative chemical. CHEMICAL FORMULAS
A formula is the representation of the manner in which it formed a compound. For example the formula: H2O, we say that water contains two elements hydrogen and oxygen O. H Also tells us that each water molecule has two hydrogen atoms and one oxygen atom. The formula also tells us if the atoms are bound together by shared electrons (covalent bonds) or by electrostatic attraction of oppositely charged ions (link electrovalent).
What can we do to give names to many formulas?
The first is to use an appropriate nomenclature.
To facilitate communication between the formulas was a need to develop a unique language, systematic and uniform to identify chemicals. This language has been developed by the IUPAC (International Union of Pure and Applied Chemistry), which is under constant review in order to adapt to the compounds discovered every year. There
trivial nomenclature
compounds with names that have names that do not follow IUPAC rules, these names are considered trivial or common and learned in practice and not to rules and then some compounds are noted with their most common names : H2O Water
Ammonia NH3 N2H4 Hydrazine
Alumina Al2O3 CaO
Sosa Cal
NaOH KOH caustic potash
OXIDATION NUMBER
To remember the formulas of the compounds and write properly, it is useful to use a system called oxidation oxidation numbers. The oxidation number system was developed based on the composition of the compounds, the relative electronegativities of the elements forming compounds and a set of rules and arbitrary.
Some of these arbitrary rules are: a.
The oxidation number of an uncombined element is 0. B.
In a compound, the more electronegative elements have oxidation number negative, while the less electronegative elements have positive oxidation states. C.
In each formula of a compound, the sum of the negative oxidation numbers equals the sum of positive oxidation numbers, ie the algebraic sum of oxidation numbers of a compound should always be zero because molecules are neutral.
Examples:
₊ Na 1 Cl 1
Na2SO4 ₋ Na2 ₊ ₊ 1 S 6 O 4 2
CO2 ₋ calculate the oxidation
No. 2O7 Cl calculate the oxidation
No. OF2 calculate the oxidation
No. Table periodical is a guide to establish some criteria that will be useful for predicting the No. oxidation of the elements, according to the group to which they belong. Consider the following table:
GROUP IA IIA IIIA IVA VA VIA VIIA
No. oxidation
ng +1 +2 +3 +4 +5 +6 +7 +2 +3 +4 +5
2 +1
+1 +2 +3 4 3 2 1
As shown, the IA group elements always have oxidation number of +1, (hydrogen when combined with metals have oxidation number 1, but when combined with nonmetals its oxidation number is +1).
in group VIA is the oxygen that is always a Oxidation number of 2 (only in the peroxide oxidation number is 1).
also shows that the elements of groups IVA, VA, VIA and VIIA, has variable oxidation numbers. This is because certain elements give or share electrons in several ways.
For example, the Fe (has variable oxidation number like other transition elements) shows the oxidation numbers of +2 and +3. To avoid ambiguity in the names of the compounds, indicating the number of oxidation with Roman numerals.
iron II chloride FeCl2 FeCl3
iron III chloride
iron II sulphate FeSO4
This type of nomenclature is very recent so in most texts, the standard nomenclature is a bit different. A compound of an element with lower oxidation number is given and the termination bear higher oxidation numbers given termination ico. Ferrous chloride
FeCl2 FeCl3 Ferric Chloride Ferrous Sulfate FeSO4
Fe 2 (SO4) 3
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