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1. Lower Ionisation energy of metals. 

2. Higher Electron affinity of non – metal 

3. Higher magnitude of lattice energy of bond 

4. Higher electromagnativity difference between metal and non-metals. 

5. Larger radius of cation of smaller radius of anion.

Because Alkali metals have low first ionization energy while halogens have high electron affinity.

(a) A pair of electrons which is not shared by any other atom is called lone pair of electrons.The electrons of valence shell shared by two atoms to form a covalent bond are called shared pair of electrons.

(b)(i) Calcium and oxygen make up Calcium oxide. Calcium needs to lose 2 electrons while oxygen needs to gain 2 electrons to complete octet structure. ii) Two atoms of hydrogen and an atom of oxygen make up water molecule. .Hydrogen atoms need to gain one electron to complete its duplet while oxygen needs to gain 2 electrons to complete octet structure.

(ii) In carbon tetrachloride, there is one carbon and 4 chlorine atoms. Each of the four chlorine atoms needs to gain one electron to complete its octet while carbon needs to gain 4 electrons to complete octet state.

(a) Unequal, polar

(b) Middle, equally

(c) Electrovalent, electrostatic

The correct answer is (ii) 120°

(ii) O₂^– < O₂ < O₂⁺

The correct answer is (i) A

(iv) The order of energies of molecular orbitals in N₂ molecule is

σ2s < σ* 2s < σ2p_z < (π2p_x = π2p_y ) < (π* 2p_x = π* 2p_y) < σ*2p_z

The correct answer is (ii) C₂

(i) (π2p_y ) < (σ2p_z) < (π*2p_x) ≈ (π*2p_y)

The correct answer is (iv) BC₃

(ii) Covalent

The chemical bond formed between two atoms as a result of the transfer of one or more electrons from one atom to the other is called ionic bond. Such a bond is possible only between atoms of different nature, one atom should have the tendency to lose electron or electrons and other atom should have the tendency to accept electron or electrons. Points of difference: (i) Ionic bond is possible between dissimilar atoms i.e., on electropositive and other electronegative atom while the covalent bond is possible between similar as well as dissimilar atoms. (ii) Ionic bond is non-rigid and non-directional. It does not show isomerism while covalent bond is rigid and directional and can cause space isomerism. 

(iii) O₃

(iv) NO₂

(i), (ii)

(i) CN^–

(ii) NO⁺

(i) NO⁺

(ii) N₂

(i) BeCl₂  

(iv) CS₂

It is a process where two or more atomic orbital of comparable energy of valency shell of an atom mix to form the same number of new orbital of same energy.

D) both B and C

Three pairs.

• Each covalent bond is formed as a result of sharing of electron pair between the two atoms.
• When a covalent bond is formed, each combining atom contributes one electron to the shared pair.
• The combining atoms attain the outer shell noble gas configuration as a result of the sharing of electrons.

In NH₄⁺,

Nitrogen atom (N) will have formal charge of +1.

Correct option is  B) Co^- 

In compounds like KCl, MgCl₂, CaO, NaF, etc, 

The constituent atoms complete their octet by lose or gain of electrons.

e.g. K → K⁺ + e^-

Cl + e^- → Cl^-

K⁺ + Cl^- → KCl

[Note : Students are expected to search more atoms on their own.]

i. Significance : 

Octet rule is found to be very useful :

• in explaining the normal valence of elements
• in the study of the chemical combination of atoms leading to the formation of molecule.

ii. Octet rule is not valid for H and Li atoms. 

According to octet rule, during the formation of a chemical bond, each atom loses, gains or shares electrons so that it achieves stable octet (eight electrons in the valence shell). 

However,

H and Li atoms tend to have only two electrons in their valence shell similar to that of Helium (1s²), which called duplet.

Hence,

Octet rule is not valid for H and Li atoms.

Correct option is  D) Al

By sharing of electrons

Answer is 1 electrons

Sodium donates one electron to chlorine to become sodium ion [Na⁺] and chlorine become chloride ion [Cl]

The stability of an ionic compound is measured by the amount of energy released during lattice formation.

Born-Haber cycle.

i. In the BF₃ molecule,

The central boron atom undergoes sp² hybridization giving rise to three sp² hybridized orbitals directed towards three comers of an equilateral triangle. 

Thus, 

The geometry is trigonal planar.

ii. In the NH₃ molecule, 

The central nitrogen atom undergoes sp³ hybridization giving rise to four sp³ hybridized orbitals directed towards four comers of a tetrahedron. 

The expected geometry of NH₃ molecule is regular tetrahedral with bond angle 109°28′. 

There is one lone pair of electrons in one of the sp³ hybrid orbitals of nitrogen. 

The lone pair-bond pair repulsion distorts the bond angle.

Hence,

The structure of NH₃ is distorted and it has pyramidal geometry.

The energy required when one mole of an ionic compound in crystalline form is split into the constituent ions is called lattice enthalpy. 

a. In acetylene molecule,

There are five covalent bonds.

b. In acetylene molecule,

There are three sigma bonds and two pi bonds. 

c. In acetylene molecule,

Each carbon atom undergoes sp hybridization.

a. Bond Enthalpy : 

Bond enthalpy is defined as the amount of energy required to break one mole of a bond of one type, present between two atoms in a gaseous state.

b. Bond Length : 

Bond length is defined as the equilibrium distance between the nuclei of two covalently bonded atoms in a molecule.

a. When unsaturation increases, the bond length decreases.

b. The stable compound is ethyne (C₂H₂).

c. Bond strength ∝ Bond enthalpy

Larger the bond enthalpy, stronger is the bond.

d. As bond length decreases, bond enthalpy, bond strength and stability increase.

a. CF₄ :

There are four bond pairs on the central atom.

Hence,

Shape of CF₄ is tetrahedral and F-C-F bond angle is 109° 28′.

b. NF₃ :

There are three bond pairs and one lone pair on the central atom. 

Hence,

Shape of NF₃ is trigonal pyramidal and F-N-F bond angle is less than 109° 28′.

c. HCN :

There are two bond pairs on the central atom. 

Hence, 

Shape of HCN is linear and H-C-N bond angle is 180°.

d. H₂S :

There are two bond pairs and two lone pairs on the central atom. 

Hence, 

Shape of H₂S is bent or V-shaped and H-S-H bond angle is slightly less than 109° 28′.

(c) s, p_x, p_y, p_z, d_x²-y²  

PCl₅ – sp³d hybridisation s, p_x, p_y, p_z, d_x²-y²

In BrF₅ there are 5 bonded pairs of electrons & one lone pair of electrons, therefore, it is square pyramidal.

KF forms H-bond with HF while KCl cannot form H-bond with HCl.

An ionic bond (or electrovalent bond) is formed by a complete transfer of one of outer most electrons from the atom of a metal to that of a non – metal.

AsF5: 

Trigonal bipyramidal molecule: As has five electrons in its outermost orbit. Due to sharing of 5 electrons from 5 F-atoms, there are in all 5 electron pairs. These are distributed in space to form a trigonal bypyramid

SiCl₄: A tetrahedral molecule. Si has 4 electrons in its outermost shell. Due to mutual sharing of electrons with Cl there are 4 electron pairs around Si. To keep the repulsion at the minimum, these 4 electron pairs should be arranged in a tetrahedral manner around Si. Thus, SiCl₄ is a tetrahedral molecule.

(d) sp³d, sp³ and sp² hybridised respectively

CIF₃ – sp³d hybridisation

NF₃ – sp³ hybridisation 

BF₃ – sp² hybridisation

All these molecules/ions have zero dipole moment.

The atoms tend to adjust the arrangement of their electrons in such a way that they (except H and He) achieve eight electrons in their outermost shell. This is known as the octet rule.