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Hydrogen – Each of the two H atoms contributes one electron so as to have one shared pair of electrons between them.Both atoms attain stable – duplet structure, resulting in the – formation of a -single covalent bond [H-H] between them.

Chlorine – Each of the two Cl atoms contributes one electron so as to have one shared pair of electrons between them. Both atoms attain stable – octet structure, resulting in the – formation of a – single covalent bond [Cl – Cl] between them.

Oxygen – Each of the two O atoms contributes two electron so as to have two shared pair of electrons between them. Both atoms attain stable – octet structure, resulting in the – formation of a – double covalent bond [O = O] between them.

Nitrogen-  Each of the two N atoms contributes three electron so as to have three shared pair of electrons between them. Both atoms attain stable – octet structure, resulting in the – formation of a – tripple covalent bond [N = N] between them.

(1) Covalent bond : The chemical bond formed due to mutual sharing of electrons between the given pairs of atoms of non-metallic elements. In the bond formed by a shared pair of electrons, each bonding atom contributing one electron to the pair. Depending on number of electron pairs shared bond is single [-], double [=], or triple [ = ] covalent.

(2) Covalent compound : The chemical compound formed due to mutual sharing of electrons between the given pairs of atoms forming a covalent bond is called covalent compound.

(3) Covalency : The number of electron pairs which an atom shares with one or more atoms of the same or different kind to achieve stable electronic configuration is called covalency.

(4) Shared pair of electrons : A pair of electrons which is shared between two atoms resulting the formation of a covalent bond is called a shared pair of electrons.

(a) Formation of Hydrogen molecule (H₂ ) (Non-polar covalent compound).

Atom ₁¹H – it needs one electron to achieve a stable configuration

1. Electron Dot Structure

2. Atomic or orbit structural diagram

(b) Formation of Chlorine (Cl₂ ) (non-polar covalent compound)

Chlorine atom Cl electronic configuration (2,8,7)— It needs one electron to attain stable configuration

1. Electron Dot Structure

2. Atomic or orbit structural diagram 

(c) Formation of Oxygen molecule (O₂) 

Oxygen atom  ₈¹⁶O electronic configuration 2,6 When two oxygen atoms contributes two electrons so as to have two shared pair of electrons between them hereby both atoms attain stable octet structure resulting in the formation of double bond [O = O] between them.

1. Electron Dot Structure

2. Atomic or orbit structural diagram 

(d)  Formation of Nitrogen Molecule (N₂ ) (non-polar covalent compound) Nitrogen electronic configuration (2,5). When two nitrogen atoms come close, each contributes three electrons to share to attain stable octet structure resulting in formation of triple bond (N = N) – N₂ .

1. Electron Dot Structure

2. Atomic or orbit structural diagram

(e) Formation of Water molecule (H₂O) Hydrogen ¹₁H electronic structure 1.

Oxygen ₈¹⁶O electronic structure 6 needs two electrons to complete octet. When a molecule of water is formed, each of two hydrogen atoms share one electron pair with oxygen atom.

1. Electron Dot Structure

2. Atomic or orbit structural diagram 

(f) Formation of Methane moleucle (CH₄ ) Carbon atom ₁₂⁶C electronic configuration (2,4) Hydrogen ₁¹H

When a molecule of methane is formed one atom of C shares four electron pairs, one with each of four atoms of Hydrogen

1. Electron Dot Structure

2. Atomic or orbit structural diagram 

(g) Formation of Carbon Tetrachloride (CCl₄) Carbon ₁₂⁶C (2,4) Carbon needs- four electrons to attain – stable octet. Chlorine ³⁵₁₇Cl (2,8,7) Chlorine needs – one electron to attain – stable octet.

1. Electron Dot Structure

2. Atomic Or orbit Structural Diagram

(h) Formation of Ammonia molecule (NH₃)

Electronic configuration of H (Z = 1) and N (Z = 7) are

K L

H(Z= 1): 1,

N(Z=7):2 5

Hydrogen has one electron in its outermost shell and nitrogen has five electrons in its outermost shell.

1. Electron dot diagram 

2. Atomic or orbital structural diagram 

(i) Atomic or orbital structural diagram 

Carbon – C (2,4) Carbon needs- four electrons to attain – stable octet. Oxygen O (2, 6) Oxygen needs – two electron to attain – stable octet.

1. Electron Dot Structure

2. Atomic or orbit structural diagram

It has been found that a methane molecule has a three dimensional tetrahedral structure. The four carbon hydrogen tetrahedral structure. The four carbon hydrogen bonds are directed towards the four corners of tetrahedron. In such a configuration, none of the participating atoms is more electrically charged as compared to other atoms. Hence methane molecule is a non polar covalent compound. 

(a) Properties of Ionic Compounds:

1. Ionic compounds usually exist in the form of crystalline solids.

2. Ionic compounds have high melting and boiling points.

3. Ionic compounds are generally soluble in water but insoluble in organic solvents.

4. They are good conductors of electricity in the fused or in aqueous solution state.

(b) Properties of Covalent Compounds:

1. The covalent compounds exist as gases or liquids or soft solids.

2. The melting and boiling points of covalent compounds are generally low.

3. Covalent compounds are insoluble in water but dissolve in organic solvents.

4. They are non-conductors of electricity in solid, molten or aqueous state.

Conditions for formation of Ionic bond are:

(i) The atom which changes into cation should possess 1, 2 or 3 valency electrons. The other atom which changes into anion should possess 5, 6 or 7 electrons in the valence shell.

(ii) A high difference of electronegativity of the two atoms is necessary for the formation of an Ionic bond.

(iii) There must be an overall decrease in energy i.e., energy must be released.

For this an atom should have low value of Ionisation potential and the other atom should have high value of electron affinity.

(iv) Higher the lattice energy, greater will be the case of forming an ionic compound

Since M combines with oxygen to form MO which means that M has a valency of +2. Hence, the formula of the compounds with chlorine and sulphur are: MCl2 and MS.

(a) A chemical bond may be defined as the force of attraction between any two atoms, in a molecule, to maintain stability.

(b) The chemical bond formed between two atoms by transfer of one or more electrons from the atom of a metallic electropositive element to an atom of a non-metallic electronegative element.

(c) The chemical bond formed due to mutual sharing of electrons between the given pairs of atoms of non-metallic elements.

The correct answer is:- (d) CCl₄

(D) Ionizes when dissolved in water.

(a)(i) D

(b)

(i) Covalent bond

(ii) Coordinate bond.

(a) HCl and H₂O

(b) H⁺ and Cl^- ions

And

H⁺ and O^2- ions

In the Lewis description of covalent bond, the Bond Order is given by the number of bonds between the two atoms in a molecule 

Resonance: Whenever a single Lewis structure cannot describe a molecule accurately, a number of structures with similar energy, positions of nuclei, bonding and non bonding pairs of electrons are taken as the canonical structures of the hybrid which describes the molecule accurately.

Some salient features of electrovalency are mentioned below :

(i) An electrovalent bond is formed by loss or gain or transfer of electrons.

(ii) Ions are formed during the formation of an electrovalent bond.

Positive ions → Cations (Na⁺ , K⁺ , Ca²⁺ , etc.)

Negative ions → Anions (Cl^– , O^2- , N^3- , etc.)

(iii) An electrostatic force of attraction exist between the oppositely charged ions.

(iv) There is one fixed direction in space among the ions. 

(i) It cannot explain the formation of molecules like BeF₂ , BF₃ in which the central atom has less than 8 electrons in its valence shell.

(ii) It cannot explain the formation of molecules such as PF₅ , SF₆ etc., in which central atom has more than eight electrons in its valence shell.

The general characteristics of electrovalent compounds are:

(i) Electrovalent compounds are mostly crystalline in nature.

(ii) Electrovalent compounds form hard crystals. These crystals are usually brittle. 

(iii) Electrovalent compounds have high density with high melting and boiling points. 

(iv) Electrovalent compounds are soluble in polar solvents.

(v) Electrovalent compounds exhibit isomorphism.

(vi) They react very fast.

The formation of an ionic compound depends on the following factors:

(i) Low ionisation energy: Lesser is the ionisation energy of an atom, greater will be its tendency to form cation by losing the valence electron. Metals with lower ionisation energy values have a greater tendency to form ionic bonds.

(ii) High electron affinity: Higher the value of electron affinity, greater will be the tendency of the atom to gain electron and form an anion. Elements with high electron affinity values form ionic compounds.

(iii) High lattice energy: The higher is the value of lattice energy, greater will be the electrostatic force of attraction between the oppositely charged ions and hence ionic compounds are formed with greater ease by release of energy. 

2 electrons in the outer shell of a nitrogen atom are not involved in the formation of a nitrogen molecule.

There is a mutual sharing of electrons.

The important general characteristics of covalent compounds are as follows:

(i) Usually covalent compounds exist in gaseous, liquid or amorphous state.

(ii) Covalent compounds have low melting or boiling points.

(iii) Except for graphite, covalent compounds are bad conductors of electricity.

(iv) Covalent compounds are soluble in non polar solvents (usually organic solvents). Polar cgvalent compounds are however soluble in polar solvents.

(v) Covalent compounds contain molecules and they undergo reactions slowly.

(vi) Many covalent compounds exhibit various types of isomerism.

Cation and anion 

(i) Ions

(ii) Electrons are shared between the atoms of two or more elements

(iii) Two

(iv) Magnesium is oxidized and chlorine is reduced

pi (π) – bond is always present in molecules containing multiple bond.

A covalent bond formed by the mutual sharing of three pair of electrons is called a triple covalent bond, or simply a triple bond. A triple covalent bond is represented by three small horizontal lines (≡) between the two atoms. 

E.g. N≡N, H-C≡C-H etc.

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

The product of the magnitude of the charge and the distance between the centres of positive and negative charge. It is a vector quantity and is represented by an arrow with its tail at the positive centre and head pointing towards a negative centre. 

Dipole moment (μ) = charge (Q) × distance of separation (r)

It is defined as the angle between the orbitals containing bonding electron pairs around the central atom in a molecule/complex ion.

Sodium, chlorine

i. In the BeF₂ molecule,

The central beryllium atom undergoes sp hybridization giving rise to two sp hybridized orbitals placed diagonally opposite with an angle of 180°. 

Thus,

F-Be-F is a linear molecule.

ii. In the H₂O molecule,

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

There are two lone pairs of electrons in two of the sp³ hybrid orbitals of oxygen.

The lone pair - Ione pair repulsion distorts the structure.

Hence,

H-O-H is angular or V-shaped.

Atoms with half-filled or vacant orbitals try to get paired electrons in those orbitals by bond formation, i.e. by losing, gaining or sharing of electrons.

It is defined as the amount of energy required to break one mole of bonds of a particular type between two atoms in a gaseous state.

(a) X has 7 electrons in its outermost shell and Y has only one electron in its outermost shell so Y loses its one electron and X gains that electron to form an ionic bond.

(b) The formula of the compound would be XY.

There are 1 outermost shell of sodium atom

The energy associated when are mole of ionic crystal is formed from its gaseous ions.

Valence electrons present in the outermost shell.

i) In BaCl₂ – Ionic. 

ii) In C₂H₄ – Covalent (double bond H₂C = CH₂)

There are 7 electrons in outermost shell of chlorine.

1. Electrolytes produce ions in solution, which carry current. 

2. Ionic compounds in the fused state and aqueous solutions contain ions moving freely. Hence they conduct electricity.

The electronic configuration of Fluorine 2, -7

Answer is NO.

9 atomic number of fluorine

Ionic bond is readily formed between atoms of elements with a low ionisation energy and atoms of elements with high electronegativity.

It is the number of covalent bonds holding the atoms in the molecule. 

Example: If the bond is formed by the sharing of two electron pairs, then the bond order is 2. O = O or C = C bond in alkenes.

Due to resonance.

It is defined as “the amount of energy required to break one mole of bonds of a particular type in the gaseous state.” It is also called bond dissociation enthalpy. 

Example: C – C bond enthalpy is 348 kJ mol^-1.

a) Sodium, one electron 

b) Chlorine, one electron

Ionic bond is a chemical bond formed by electron transfer in an ionic bond, the ions are held together by the electrostatic force of attraction between the oppositely charged ions.

A bond formed between two atoms by the sideways overlapping of two half filled p-orbitals is called as a pi bond.

It is the angle subtended by two imaginary lines that pass from the nuclei of two atoms which form the covalent bonds with the central atom through the nucleus of the central atom at the central atom.

Bond lengths and bond energies are not same when the atoms that form the bond are different.