Explore topic-wise InterviewSolutions in .

Correct option is  B) H₂O

B) BeCl₂ , BF₃ , CH₄ , NH₃

Correct option is  A) H₂O

D) Tetrahydral

Correct option is  A) BeCl₂

Correct option is  C) Pyramidal

The cause of chemical combination between atoms of the various elements is their tendency to acquire nearest stable noble gas configuration of octet of electrons and duplet of electrons in case of hydrogen atoms in their outermost shells. 

When the unshared pair of electrons around an atom in the middle of a molecule is completely shared by another atom or an ion, it is called lone pair effect. Lone pair effect is shpwn by polar covalent compounds such as HCl and NH₃ .

+1

Formal charge on triply bonded oxygen atom

= N_v - \(\Big[N_l+\frac{N_b}{2}\Big]\) = 6 - \(\Big[2+\frac{6}{2}\Big]\)= 6 - 5 = +1

(i) Ionic bond 

(ii) Covalent bond 

(iii) Co-ordinate bond 

(iv) Hydrogen bond 

(v) Metallic bond

Ionic, Co-ordinate & Covalent bonds are present inNH₄Cl.

The concept of hybridization was introduced because the valence bond theory failed to explain the following points :

i. Valencies of certain elements :

The maximum number of covalent bonds which an atom can form equals the number of unpaired electrons present in its valence shell. However, valence bond theory failed to explain how beryllium, boron and carbon forms two, three and four covalent bonds respectively.

a. Beryllium : 

The electronic configuration of beryllium is 1s² 2s². The expected valency is zero (as there is no unpaired electron) but the observed valency is 2 as in BeCl₂.

b. Boron :

The electronic configuration of boron is 1s² 2s² \(2p^1_x\).The valency is expected to be 1 but it is 3 as in BF₃.

c. Carbon : 

The electronic configuration of carbon is 1s² 2s² \(2p^1_x\) \(2p^1_y\) . The valency is expected to be 2, but observed valency is 4 as in CH₄.

ii. The shapes and geometry of certain molecules :

The valence bond theory cannot explain shapes, geometries and bond angles in certain molecules, 

e.g. 

a. Tetrahedral shape of methane molecule. 

b. Bond angles in molecules like NH₃(107°18′) and H₂O (104°35′).

However,

The valency of the above elements and the observe structural properties of the above molecules can be explained by the concept of hybridization. 

These are the reasons for need of the concept of hybridization.

The general characteristics 

(i) Co-ordinate compounds are identical to normal covalent compounds.

(ii) It is rigid and has directional properties. 

(iii) These compounds are soluble in non-polar solvents and insoluble in polar solvent. 

(iv) These compounds behave as non-conductors of electricity.

(v) The melting and boiling points are higher than covalent compounds and lower than ionic compounds.

(vi) These are stable compounds

The bond formed by donation of electron from one of the constituents present in the molecule is called co-ordinate bond. 

It is only directional bond & indicated by ” → ” 

H₃ → BF₃ [Nitrogen donates pair of electrons to form bond] NH₃BF₃

The dipole moment of the polyatomic molecule depends on individual dipole moments of bonds and also on the spatial arrangement of various bonds in the molecule.

1. Atomic size 

2. Ionisation potential 

3. Electron affinity 

4. Electronegativity

Correct option is  C) a, b, c, d

Some compounds and their nature are shown in table complete the table by finding out the electron negativity difference between the constituent elements.

Generally, the electronegativity difference of the component elements in a compound is 1.7 or more it shows ionic character. If it is less than 1.7 it shows covalent character

A) greater than or equal to 1.9

(i) SO₂ 

Electronegativity difference = 3.5 – 2.58 = 0.92 

If the electronegativity difference is less than 1.7, it shows covalent character. 

(ii) Water (H₂O)

Electronegativity difference = 3.5 – 2.2 = 1.3

If the electronegativity difference is less than 1.7 it forms covalent compounds. 

(iii) CaF₂ 

Electronegativity difference = 3.98 -1.0 = 2.98 

If the electronegativity difference is greater than 1.7 if forms ionic compounds. 

(iv) CO₂ 

Electronegativity difference = 3.5 – 2. 5 = 1.0 

If the electronegativity difference is less than 1.7 it shows covalent compounds.

The compounds are covalent.

Properties of covalent compounds : 

1. Covalent compounds are usually liquids or gases, only some of them are solids. 

2. The covalent compounds are usually liquids or gases due to the weak force of attraction between their molecules. 

3. Covalent compounds have usually low melting and low boiling points.

4. Covalent compounds are usually in soluble in water but they are soluble in organic solvents. 

5. Covalent compounds do not conduct electricity. 

Uses of covalent compounds : 

1. Covalent compounds form 99% of our body. 

2. Water is a covalent compound. We know its many uses. 

3. Sugars, food substances, tea and coffee are all covalent compounds. 

4. Air we breathe in contains covalent molecules of oxygen and nitrogen. 

5. Almost everything on earth other than most simple in organic salts are covalent

Correct option is  D

D) All of these

(a) bonding and antibonding molecular orbital:

(b) Molecular orbital configuration of N₂:

(σ1s)²(σ*1s)²(σ2s)²,(σ*2s)²(π2p_x)² = (π2p_y)²,(σ2p_z)²

Bond order = \(\frac{1}{2}\)(\(N_b-N_a\))

= \(\frac{1}{2}\) (10 - 4) = 3

Magnetic behavior - Diamagnetic due to absence of unpaired electrons.

(b) Both (A) and (R) are correct and (R) is the correct explanation of (A).

(a) Sodium atom and sodium ion

(i) Sodium atom has one electron in M shell while sodium ion has 8 electrons in L shell.

(ii) Sodium atom is neutral while sodium ion is positively charged.

(iii) Sodium atom is highly reactive while its ion is inert.

(iv) Sodium atom is poisonous while sodium ion is non-poisonous.

(b) Chlorine atom and chlorine ion

(i) Chlorine atom has 7 electrons in its M shell while Chloride ion has 8 electrons in the same shell.

(ii) Chlorine atom is neutral while chloride ion is negatively charged.

(iii) Chlorine atom is highly reactive while its ion is inert.

(iv) Chlorine gas is poisonous while chloride ion is non-poisonous.

Answer is 1 valencies

The main postulates of VSEPR theory are as follows : 

(i) The shape of a molecule depends upon the number of valence shell electron pairs around the central atom. 

(ii) Pairs of electrons in the valence shell repel one another since their electron clouds are negatively charged. 

(iii) There pairs of electrons tends to occupy such position in space that minimize repulsion and thus maximize distance between them. 

(iv) The valence shell is taken as a sphere with the electron pairs localizing on the sphere at maximum distance from one another. 

(v) A multiple bond is treated as it is a single electron pair and two or three electron pairs of a multiple bond is treated as super pair. 

(vi) When two or more resonance structures can represent a molecule, the VSEPR nodal is applicable to any such structure.

The answer is (a) NO

Lone pair electrons do not take part in bond formation whereas bond pair electrons take part in bond formation.

Correct option is  B) 3

The valency of oxygen is 2. 

So the valency of carbon = 2 × 2 = 4.

The formula of carbon tetra chloride is CCl₄ . The valency of chlorine is 1. So the valency of carbon is 4.

(i) X X²⁺+2e-

Y + 3e- Y^3-

(ii) 6X+2Y₂ 2X3Y₂

(iii) cathode , anode

a) The valence electrons in Y are 5. 

b) The valency of Y is 3. 

c) The valency of X is 1. 

d) There are three covalent bonds. 

e) The element Y is Nitrogen and X is Hydrogen.

1. The ability of a cation to polarise an anion is called its polarising ability and the tendency of an anion to get polarised is called its polarizability. The extent of polarisation in an ionic compound is given by the Fajans rule

2. To show greater covalent character, both the cation and anion should have high charge on them. Higher the positive charge on the Cation greater will be the attraction on the electron cloud of the anion.

Similarly higher the magnitude of negative charge on anion, greater is its polarizability. For example, Na⁺ < Mg²⁺ < Al³⁺ , the covalent character also follows the order – NaCI < MgCl₂ < AICI₃

3. The smaller cation and larger anion show greater covalent character due to the greater extent of polarisation. e.g., LiCl is more covalent than NaCI.

4. Cation having ns² np⁶ nd¹⁰ configuration shows greater polarising power than the cations with ns² np⁶ configuration. e.g., CuCI is more covalent than NaCl.

The correct answer is (iii) H₂O 

Covalent bond.

Ionic bond is formed between the atoms having different electronegativity.

Electrovalent or ionic bond.

O-O bond lengths in ozone molecule are equal because of resonance between its structures.

C₂H₄ shows sp² hybridization and thus 1s coplanar whereas C₂H₂ show sp hybridization and thus linear.

The correct option is- (b) sp

sp

Hybridisation which takes place in acetylene is sp.

The correct answer is-(a) XeF₂

₁₆S = 2, 8, 6 = 1s² , 2s²2p² , 3s²3p⁴ S contains 6 valence electrons, all these 6 electrons are used to form bond with six F atoms. So, it has six bond pairs. No of lone pairs = Valence electrons-bond pairs

= 6 - 6

= 0

sp³d²

The type of hybridisation takes place in SF₆ is sp³d².

4

The number of lone pair of electrons on C – atom present in CO₂ are 4.

90º

In SF₆ , the bond angle is 90º .