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Read the passage given below and answer the following questions from (i) to (v).

The attractive force which holds variousconstituents (atoms, ions, etc.) together in differentchemical species is called a chemical bond. In order to explain the formation of chemicalbond in terms of electrons, a number ofattempts were made, but it was only in 1916 when Kössel and Lewis succeededindependently in giving a satisfactoryexplanation. They were the first to providesome logical explanation of valence which wasbased on the inertness of noble gases. Lewis postulated that atoms achieve thestable octet when they are linked bychemical bonds. In the formation of amolecule, only the outer shell electrons takepart in chemical combination and they areknown as valence electrons. The inner shellelectrons are well protected and are generallynot involved in the combination process.G.N. Lewis, an American chemist introducedsimple notations to represent valenceelectrons in an atom. These notations arecalled Lewis symbols. For example, the Lewissymbols for the elements of second period areas under:
The bond formed, as a result of theelectrostatic attraction between thepositive and negative ions was termed as the electrovalent bond. The electrovalenceis thus equal to the number of unitcharge(s) on the ion.
Kössel and Lewis in 1916 developed animportant theory of chemical combinationbetween atoms known as electronic theoryof chemical bonding. According to this,atoms can combine either by transfer ofvalence electrons from one atom to another(gaining or losing) or by sharing of valenceelectrons in order to have an octet in theirvalence shells. This is known as octet rule. when two atoms share oneelectron pair they are said to be joined bya single covalent bond. In many compoundswe have multiple bonds between atoms. Theformation of multiple bonds envisagessharing of more than one electron pairbetween two atoms. If two atoms share twopairs of electrons, the covalent bondbetween them is called a double bond. Forexample, in the carbon dioxide molecule, wehave two double bonds between the carbonand oxygen atoms. Similarly in ethenemolecule the two carbon atoms are joined bya double bond. The Lewis dot structures provide a pictureof bonding in molecules and ions in termsof the shared pairs of electrons and theoctet rule. The Lewis dotstructures can be written by adopting thefollowing steps:
- The total number of electrons required forwriting the structures are obtained byadding the valence electrons of thecombining atoms. For example, in the $CH _4$ molecule there are eight valence electronsavailable for bonding.
- For anions, each negative charge wouldmean addition of one electron. Forcations, each positive charge would result in subtraction of one electron from the totalnumber of valence electrons. For example,for the $CO _3{ }^{2-}$ ion, the two negative chargesindicate that there are two additionalelectrons than those provided by theneutral atoms.
- Knowing the chemical symbols of thecombining atoms and having knowledgeof the skeletal structure of the compound, it is easyto distribute the total number of electronsas bonding shared pairs between theatoms in proportion to the total bonds.
- In general the least electronegative atomoccupies the central position in themolecule/ion. For example in the $NF _3$ andCO ${ }_3{ }^{2-}$, nitrogen and carbon are the centralatoms whereas fluorine and oxygenoccupy the terminal positions.
- After accounting for the shared pairs ofelectrons for single bonds, the remainingelectron pairs are either utilized for multiplebonding or remain as the lone pairs. Thebasic requirement being that each bondedatom gets an octet of electrons.
i. ... postulated that atoms achieve the stable octet when they are linked by chemical bonds.

1. … postulated that atoms achieve the stable octet when they are linked by chemical bonds.

1. Lewis
2. Debye
3. Charles
4. Sidgwick

2. … in 1916 developed an important theory of chemical combination between atoms known as electronic theory of chemical bonding.

1. Kössel
2. Lewis
3. Both a) & b)
4. Sidgwick

3. In the formation of a molecule, only the outer shell electrons take part in chemical combination and they are known as …

1. Backscattered electrons
2. Valence electrons
3. Primary electrons
4. Secondary electrons

4. In the $CH_4$​​​​​​​ molecule there are … valence electrons available for bonding.

1. 4
2. 6
3. 8
4. 10

5. The type of bond between atoms in a molecule of CO2 is:

1. Ionic bond
2. Metallic bond
3. Hydrogen bond
4. Covalent bond.