Class 11 Chemistry Chemical Bonding Important MCQs with Brief Answers for Exams:

1.Atoms form chemical bond to become:

1.Reactive

2.Conductive

3.Soluble

4.Stable

Answer )  Stable

Brief Explanation :

Atoms form chemical bond to complete their valence shells like inert gases and becomes stable .The inert gases are stable and non-reactive due to their complete valence shells .

All other known elements tend to complete their Valence shells by re-arrangement (transfer, sharing or donation) of electrons and become stable.

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2. A covalent bond is formed by the            of electrons:

1.Complete transfer

2.Equal sharing

3.Unequal sharing

4.Both 2 & 3

Answer ) Both 2 & 3

Brief Explanation :

A covalent bond is formed by the equal (i.e. non-polar)  & unequal (i.e.  polar) sharing of electrons between atoms.

When electronegativity difference two bonded atoms is zero,  the bond is non-polar like H – H , Cl – Cl bonds.

When the E.N difference is 1.7, the bond is 50% covalent and 50% ionic .

If the E.N difference is less than 1.7, the bond is more than 50% covalent & less than 50% ionic like H-CL (3.0-2.1= 0.9) & H-OH (3.5-2.1=1.4) bonds.

Similarly , a bond is more than 50% ionic & less than 50% covalent when E.N difference is more than 1.7. For example , H-F (4-2.1= 1.9) bond.

The percent ionic character of bond b/w two atoms “A” & “B” having E.N of XA & XB respectively ,can be calculated by using the Hanny – Smyth equation i.e. 

 % Ionic character  = 16 (XA –XB) + 3.5 ( XA –XB)²

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3. The strength of covalent bond depends on:

1.Nature of overlapping

2.Extent of overlapping

3.Geometry of molecule

4.Both 1 & 2

Answer ) Both 1 & 2

Brief Explanation :

The nature of the covalent bond depends upon the nature & the extent of overlapping of orbitals.

Head-on overlapping of orbitals produces strong sigma bond while sidewise overlapping produces weaker pi-bond .

Greater the extent of overlapping of orbitals , stronger is the resulting bond and vice versa.

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4. Ionic bond is formed between metals and non-metals when the difference of E.N is:

1.Zero

2.1.7

3.2 or more

4.None of these

Answer ) 2 or more

Brief Explanation :

When electronegativity difference b/w two bonded atoms is two or more , the bond is ionic .

For example ,   Na⁺ Cl^– ( 3- 0.93= 2.04)   &

                             Ca⁺O^– (3.5-1.00= 2.5)bonds.

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5. A bond which is formed by the unequal sharing of electrons:

1.Metallic

2.Polar covalent

3.Non-polar covalent

4.Co-ordinate covalent

Answer ) Polar covalent

Brief Explanation :

Polar covalent bond is formed when the atoms with different electronegativities shared electrons in covalent bond . The bonded electrons are unequal shared in a polar covalent bond.

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6. The dots & crosses surrounding a symbol in the Lewis structure represents:

1.Bonding electrons

2.Non-Bonding electrons

3.Unpaired electrons

4.Valence electrons

Answer ) Valence electrons

Brief Explanation :

A Lewis structure consists of the symbols of an element, which is surrounded by dots and crosses . The symbol represents the nucleus and the normally filled inner shells of electrons while the dots or crosses represents the valence electrons . The non-bonding electrons are usually given in pairs.

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7. VSEPR theory explains which properties of covalent molecules:

1.Geometrical shapes

2.Sharing of electrons

3.Magnetic properties

4.Type of hybridization

Answer ) Geometrical shapes

Brief Explanation :

VSEPR theory explains the geometry of a covalent molecule in terms of bond angles.

The geometry of a covalent molecule depends upon the number and nature of electron –pair around the central atom.

The electron pair tend to remain at maximum angles from each other to minimize the  repulsion and get stability.

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8. The decreasing order of repulsion among electron-pair is:

1.Bond pair-Bond pair > Lone pair-Bond pair > Lone pair-Lone pair

2.Bond pair-Bond pair >Lone pair-Lone pair > Lone pair-Bond pair

3.Lone pair-Lone pair> Bond pair-Bond pair >  Lone pair-Bond pair

4.Lone pair-Lone pair > Lone pair-Bond pair > Bond pair-Bond pair

Answer ) Lone pair-Lone pair > Lone pair-Bond pair > Bond pair-Bond pair

Brief Explanation :

The lone pair of electron is attracted by only one nucleus , so it spreads out, occupies more space & exerts greater repulsion  than the bond-pair of electrons which is attracted by two nuclei. The Lone-pair push closer the bond pair  together & decrease the angles b/w them.

 The decreasing order of repulsion = Lone pair-Lone pair > Lone pair-Bond pair > Bond pair-Bond pair

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9. A molecule with only three bond-pair electrons around the central atom is:

1. Tetrahedral

2. Pyramidal

3. Trigonal Planar

4. Linear

Answer ) Trigonal Planar

Brief Explanation :

Generally, the molecules with only two , three, or four bond pairs of electrons around  the central atom have regular geometrical shapes.

For example, molecules with two , three, or four bond pairs of electrons have linear (BeCl2) , Trigonal planar (BF3 ) or tetrahedral (CH4) shapes respectively .

The molecules ( NH3 , H2O ) with both bond-pair and lone-pair have distorted/ irregular shapes. It is due to greater repulsion of lone-pair that compresses together the bond-pair.

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10. VSEPR theory fails to explain :

1.Shapes of high polar molecules

2.Shapes of transition metal complexes

3.Formation of covalent bond

4.All of these

Answer ) All of these

Brief Explanation :

VSEPR theory can’t explain how & why electrons share to form covalent bond although they repel each other . It also can’t explain shapes of transition metal complexes & shapes of molecules with highly polar bonds. For example m LiO2 should have water-like angular shape but it has linear shape.

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