What is meant by double bond or double covalent bond? Give some examples.

The bond between two atoms formed by sharing of two pairs of electrons is called a double bond. Two horizontal lines between two atoms denote a double bond, e.g., O = O(O2)

(i) Formation of oxygen molecule, O2: Oxygen atom has six electrons in its outermost shell, two short of forming a complete octet. Thus each oxygen atom in O2 shares 2 electrons with the other oxygen atom and attains stable configuration as shown:


The bond between two atoms formed by sharing of two pairs of electron

(ii) Formation of ethylene molecule (C
2H4): In ethylene two carbon atoms share two pairs of electrons between them and the rest two electrons on each carbon atom share one electron each with two hydrogen atoms. Thus ethylene molecule has one double bond (C = C) and four single bonds (C—H).


The bond between two atoms formed by sharing of two pairs of electron


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Glacial acetic acid is:
  • an aqueous solution of alcohol 
  • vinegar
  • an aqueous solution of acetic acid
  • 100% pure ethanoic acid.

D.

100% pure ethanoic acid.
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What is a covalent bond?


The covalent bond is said to be formed when two atoms achieve stability by sharing of an electron pair, each contributing one electron to the electron-pair. In this way, the atoms can be regarded as having acquired a noble gas configuration.

e.g.,


The covalent bond is said to be formed when two atoms achieve stabili

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What is triple bond or triple covalent bond? Explain the formation of triple bond giving two examples.

The bond formed between two atoms through the sharing of three electron pairs is called a triple bond. Three horizontal lines between two atoms denote a triple bond, e.g., nitrogen molecule is given asN≡N.

(i) Formation of N2 molecule: Nitrogen atoms have five electrons in their outermost shells. Therefore, in N2 molecules, two nitrogen atoms share 3 electrons with each other, thus acquiring the stable structure and forming a N2 molecule with triple bonds.


The bond formed between two atoms through the sharing of three electr
(ii) Formation of acetylene molecule (C2H2): In acetylene molecule, each carbon atom satisfies its valency by sharing one electron with a hydrogen atom and sharing the other three electrons with the other carbon atom as shown:


The bond formed between two atoms through the sharing of three electr

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Taking a simple example, explain how the formation of covalent bond between two atoms brings stability to the molecule formation.

Take the example of formation of hydrogen molecule. When two hydrogen atoms come close together, nucleus of one atom exerts an attractive force on the electrons of the other atom and vice versa to complete their octet. This brings the two atoms still closer and potential energy decreases. At a particular distance between the two atoms, potential energy becomes minimum. Hydrogen atoms cannot come further closer because then the repulsive forces come into operation and cause the energy to increase. This stage of minimum energy which binds the two hydrogen atoms to form a molecule is actually the covalent bond.


Take the example of formation of hydrogen molecule. When two hydrogen
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