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A radical is an atom or a group of atoms of different elements having positive or negative charge and acts as a single unit throughout the chemical reactions. They do not exist freely.
On the basis of electric properties, radicals can be classified into:
The elements fall into the zero group of the periodic table are inert gases or noble gases. They are helium, neon, argon, krypton, xenon and radon. These elements are chemically inert because of their stable electronic configuration. Among all of them, only helium contains 2 electrons in their valence shell while the remaining contains 8 electrons in their valence shell. Those elements which have 8 electrons in their valence shell and do not take part in a chemical reaction are called inert gases. The given table shows the electronic configuration of inert gases,
The arrangement of two electrons in the K-shell is said to be duplet. It is chemically inert because it has a complete number of electrons in its K-shell. Helium is a duplet as it has two electrons in K- shells. Hydrogen, Lithium, Beryllium and Boron also attains a stable electronic configuration similar to that of a helium atom. It is called duplet rule. The tendency of an atom with single shell to attain two electrons in its K- shell is called duplet rule.
Except helium, the other inert gases have 8 electrons in their valence shell. Such arrange of a stable group of 8 electrons in their valence shell is said to be octet. Some atom of elements make 8 electrons in their valenceshell by gaining, losing or sharing electrons between the combining atoms during the formation of a molecule is called octet rule.
The combining capacity of elements or the radicals with the other elements or radicals to form a molecule of an element or a compound is called valency. Numbers such as 1, 2, 3, 4, 5 and 6 represents the valency.
|Fe (Ferrum)||2 Or 3|
A radical is an atom or a group of atoms of different elements having positive or negative charge and acts as single unit throughout the chemical reactions. E.g.: Ca++, O--etc.
The radicals, which have the capacity of losing electrons and carry positive charge, are called electropositive radicals. E.g.: Ca++, Mg++, Na+, etc.
Radicals act as a charged atom and are highly unstable. So, to be a stable it wants to gain or lose the electrons. So, they contain charge.
The radicals, which have the capacity of gaining electrons and carry negative charge, are called electronegative radicals. They are also called acidic radicals or non-metalic radicals, e.g.
O-- valency (2)
NO3- valency (1)
CO3-- valency (2)
HCO3- valency (1)
The compounds which are formed by sharing electrons between two or more atoms and contain covalent bonding are called covalent compounds. E.g.:
CH4 (Methane), H2O (water) etc
The chemical bond formed by the transfer of electrons from valance shell of one atom to valance shell of another atom is called electrovalent bond and the valency is electrovalency. MgCl2, CaO, Na2O, AlCl3 are some example of compounds formed by electrovalent bond.
The covalent bond is the bond formed by sharing of a pair of electrons between two atoms each contributing equal number of electrovalent electron pair. E.g.: H2, O2, CH4, CO2, etc.
The valency of sodium is 1.
The valency of sodium is 1 because it loses 1 electron at the time chemical reaction to be stable.
The valency of argon is zero.
In the valence shell of Argon, there are eight electrons. That means it is stable by octate rule. That's why it neither gains electron nor loose electron. So, it has zero valency.
Symbolic representation of one molecule of a substance is called molecular formula. E.g. H2 denotes one molecule of hydrogen.
In Nacl the valency of sodium (Na) is 1.
In MgCl the valency of Magnesium (Mg) is 2.
In CCl4 the valency of Carbon is 4.
In AlCl3 the valency of Aluminum is 3.
The state of having two electrons in the K shell of an atom is duplet state. E.g.Helium.
The arrangement of 8 electrons in the valance shell of an atom is called octet state. E.g. Neon (Ne).
Those elements which have 8 electrons in their valance shell and are kept in the zero group of periodic table are noble gases. Their valency is zero because they are stable and do not take part in chemical combination.
If the elements have more than one valency, then it is said to be variable valency.
For e.g.: Cuprous (Cu) has 1 valency
Cupric (Cu) has 2 valency.
Nitrate → 1
Chloride → 1
Silicate → 2
Sulphate → 2
Carbonate → 2
In MgCl2, valency of Cl is 1 and valency of Mg is 2.
Electrolyte: A compound which conducts electricity in its solution is electrolyte. For e.g.: NaCl solution, HCl solution etc.
Molecular formula is the short form of a molecule which is represented by the symbol of elements present in the molecules.
The molecular formula can be of an element or a compound. For example: H2, O2, N2 etc are the molecular formula of elements. Similarly, CO2, H2O, NH3 etc are the molecular formula of the compounds.
Significance of molecular formula:
In XCl5, 1 atom of 'X' combines with 5 atoms of 'Cl'. So, the valency of 'X' in XCl5 is 5. Here, the valency of 'X' is found out by comparing it with the number of chlorine.
What is the molecular formula of the compound formed by chemical combination of hydrogen and oxygen in the proportion of 1:2 respectively?