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Academia - Collins - Pocket Scientific Dictionaries - Chemistry - English - French - Arabic Letter 1_ P


paraffin
paraffine f

paraffin. Fuel obtained from petroleum, its boiling range ranges between 160° and 250° C.
See kerosine. This name was previously given to alkane.
Paraffin wax consists of a mixture of solid hydrocarbons. It is used in making candles.


pascal
pascal m

Pascal is the unit of pressure in the International System of Units (SI). The pressure of one atmosphere is equal to about one hundred kilopascals (100kPa).
A pascal is equal to the force of one newton per square metre.


passive
passif

pregnant. Description: The metal has a surface layer of oxide that makes it non-reactive, so it is inert. Aluminum has such a layer, and iron can be given a similar layer by immersing the metal in concentrated nitric acid.


peptide
peptide m

Peptide. When two or more amino acids react together, peptides are formed. The term polypeptide is usually used when the interacting amino acids are three or more. Proteins consist of several long polypeptide chains that are often linked together in different ways. Peptides contain a peptide link.

percentage composition
Pour centage of composition

Percentage composition: It is often useful in analysis to know the proportions of the elements present in the compound. These percentages are usually expressed as a percentage:

Examples:

Durable CH4

Etin C2H2

Mass percentage of:

Hydrogen - carbon
%25 ------- %75
%8 ------- %92


By knowing the percentage composition of a compound, its empirical formula can be extracted.

Example :

If we have a known compound, its percentage composition is: C. %40 C. %12 O. %48 To know the molar ratio of the elements in the compound, we divide each number by the value of the relative atomic mass Ar of the element:

3 = 48/16 (O)
1=12/12(C)
1 = 40/40 (Ca)

The molar ratio is 1:1:3.
Therefore, the ratio of atoms is 1:1:3.
The empirical formula is: CaCO3.


period
period f

Role. The horizontal rows of elements in the periodic table are called roles. The number of floors is seven. See group.


periodic table
table for a periodic period

The periodic table The periodic table shown on page (297) shows a way to represent all the elements and show their similarities and differences.

The elements are arranged in an ascending order of atomic number (Z) when moving across the table from left to right.

Floor 3

Na 11
Mg 12
Al 13
Si 14
P 15
S 16
CI 17
Ar 18


The horizontal rows are called periods and the vertical rows are called groups. There is noble gas on the far right of each floor.

1: He is the role
2: Ne
3: Ar
4: Kr
5:Xe
6: Rn

At each stage there is a progression from metals to non-metals. Similar elements are found in a group. For example, the following elements have a similar electronic configuration and are found in the same group.

the group

Alkali minerals
Li
Na
K

Group VII

Halogens
F
CI
Br
I

The number of electrons in the shell
The outer number is similar to the group number.
For example, in group I:

2.1 Lithium
2.8.1 Sodium
2.8.8.1 Potassium

The elements between the two sets are called || And ||| Transition metals. These elements are similar in many ways, including that they produce colored compounds, have variable valency, and are often used as intermediates. Elements 58 to 71 are known as lanthanide or rare earth elements. These elements are found in soil in very small quantities only.

Elements 90 to 103 are known as actinide elements, and they include most of the common elements found in nuclear reactions. As for the elements with an atomic number greater than 92, they do not exist naturally, and they were all produced artificially by stoning other elements with particles. Plutonium is formed in nuclear reactors.

Elements with atomic numbers of 104 and above are not named after famous scientists or places. Rather, it is called in an organized manner according to its atomic number:

Element 104 is unnilquadium

un = 1
nil=0
quad = 4
Unq is its symbol

Element 118 is ununoctium

un = 1
un = 1
oct=8
Uuo is his symbol