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Number of electrons in their outermost orbit.

Yes. There is some relation to energy and bond formation between atoms.

For breaking chemical bonds between atoms in a molecule.

1. If bond dissociation energy of reactants is more than bond energy of products, then energy is absorbed in the chemical reaction. 

2. If bond dissociation energy of reactants is less than bond energy of products, then energy is released in the chemical reaction.

Because of bond energy between the atoms in a molecule.

Force of attraction between them.

i. According to the Lewis theory, bond order is given by the number of bonds between the two atoms in a molecule.

e.g.,

a. In hydrogen molecule, bond order between hydrogen atoms is one as one electron pair is shared.

b. In oxygen molecule, bond order between oxygen atoms is two as two electron pairs are shared.

c. In acetylene molecule, bond order between two carbon atoms is three as three electron pairs are shared.

ii. The isoelectronic molecules and ions have identical bond orders.

e.g., 

a. The bond order of F₂ and \(O_2^{2-}\)is one. 

b. The bond order of N₂, CO and NO⁺ is 3.

iii. As the bond order increases, the bond enthalpy increases and bond length decreases.

iv. With the help of bond order, the stability of a molecule can be predicted.

[Note : N₂ molecule has bond enthalpy of 946 kJ mol^-1. It is one of the highest for diatomic molecules.]

Ionic solids are: NaCl, CuSO₄

Diamond (sp³), graphite (sp²).

In Diamond it is Sp³

In graphite it is Sp²

(i) Sp² hybridization 

(ii) Sp² hybridization.

The bond formed when one sided sharing of electron stake place is called a coordinate bond. Such a bond is also known as dative bond. It is represented by an arrow (→) pointing towards the accept or atom. 

E.g. H_3N→BF₃

Octet rule signifies –

(i) It is useful for understanding the structures of most of the organic compounds.

(ii) It mainly applies to the second period elements of the periodic table.

Lewis postulated that atoms achieve the stable octet when they are linked by chemical bonds. He assured that atoms are positively charged centre and the outer shell that could accommodate a maximum of eight electrons. These electrons occupy the corners of a cube which surrounds the centre. Lewis introduced simple notations to represent valence electrons in an atom called Lewis symbol.

Kossel in relation to chemical bonding drew attention to the following facts – 

(i) In the periodic table, the highly electronegative halogens and the highly electropositive alkali metals are separated by the noble gases. 

(ii) In the formation of a negative ion from a halogen atom and a positive ion from an alkali metal, atom is associated with a gain and loss of an electron by the respective atoms. 

(iii) The negative and positive ions so formed attain stable noble gas electronic configurations. The noble gases have particularly eight electrons, ns² np⁶. 

(iv) The –ve and +ve ions are stabilized by electrostatic attraction.

The driving force for atoms to combine is related to the tendency of each atom to attain stable electronic configuration of nearest noble gas. For an atom to achieve stable electronic configuration it must have;Either two electrons in its outermost shell (if it is the first shell- nearest noble gas – He) – Duplet rule.

OR 

Eight electrons in its outermost shell (if it is not the first shell – all noble gases other than He have eight electrons in their outermost shell) – Octet rule.

Methods for achieving chemical bonding 

A stable electronic configuration for two combining atoms, resulting in chemical bonding between them is achieved by following two ways.

1. Electron transfer : This involves transference of valence electrons from one atom (metal) to another (non-metal) leading to the formation of electrovalent or ionic bond. This results in the formation of electrovalent or ionic compound.

2. Electron sharing : This involves sharing of pairs of electrons between two atoms (both non-metals). This leads to the formation of covalent bond. The compound so formed is called a covalent compound.

NO₃^-, BF₄^-, PF₅, IF₅, CO₂.

N in NO₃^- is sp²hybridised, B in BF₄^- is sp³hybridised, P in PF₅ is sp³d hybridized, C in CO₂ is sp hybridized.

(i) H- bonding in water molecules of ice creates a lot of vacant spaces. As, a result density of ice is less than that of water . hence, it floats on the surface of water .In winters, when the temperature is very low, generally upper layer of water in the lake freezes. The aquatic life remains protected in the water underneath. 

(ii) in the vascular plants, the movement of water through the plant;s xylem and other vessels takes place through hydrogen bonding.water molecules are not only hydrogen bonded to each other but also to the cellulose cell comprising the wall of the plant cells. As a result, capillary action is set in which allows plant to pull up water into the roots. Furthermore, hydrogen bonding can create a long chain of water molecules which can overcome the force of gravity and travel upto the high altitude of the plants 

(iii) the secondary structure of the protein involves interaction (mainly hydrogen bond) between the neighbouring polypeptide backbones which contain N-H bonded pairs and O- atoms. Consequently, H-atom bonded to N in one polypeptide backbone can form H-atom with O atom in another chain and vice-versa. Though they are relatively weak, these bonds offer a great staibility to secondary protein structure because they repeata great number of times.hydrogen bonding plays an important role in DNA base pairing

N₂ has higher bond disassociation energy than O₂ due to presence of triple bond in nitrogen whereas oxygen has double bond.

The correct answer is (ii) H₂O

The correct answer is (iii) 5, 19

The correct answer is (iii) O₂^2–

The correct answer is (iii) C₂H₄

(c) BF₃ and NO^-₂

(iii) The average formal charge on each oxygen atom is 0.67 units.

(iv) All C–O bond lengths are equal.

(iii) F₂⁺

(iv) O₂^-

The columbic force of attraction which holds the as positively charged ions together is called an ionic bond. An ionic bond is formed by the complete transfer of one or more electrons from the atom of a metal to an atom of non- metal.

Number of ions lost (gained) by atoms during the formation of ionic bond.

Low ionization energy for metals and high electron affinity of non-metals.

Correct option is  C) sp³ 

(a) sp³, (b) sp².

Correct option is  C) water

Correct option is  D) BF₃

Pyramidal and Bent structure respectively.

Ethyne and CO₂.

C) polar solvents

In 1940 by Sidgwick and Powell.

Correct option is  B) Cl-Cl

Valence Shell Electron Pair Repulsion (VSEPR) theory is based on the basic idea that the electron pairs on the atoms shown in the Lewis diagram repel each other. In the real molecule, they arrange themselves in such a way that there is minimum repulsion between them.

Correct option is  C) 4

a) Lithium is metal and chlorine is nonmetal. So the bond is ionic in nature. 

b) Lithium is metal and hydrogen is non-metal. So the bond is ionic in nature. 

c) Hydrogen and chlorine are two dissimilar non-metals. So the bond formed is polar covalent bond. 

d) Carbon and chlorine are dissimilar non-metals but electronegativity difference is less. So they form nonpolar covalent bond.

a) As we move from left to right in a period non-metallic character increases. So Z is a metal and remaining two are non-metals. Therefore between two atoms of X, there would be covalent bond. The formula of compound is X₂.

b) X is a non-metal and Z is a metal. So between these two atoms, there would be an ionic bond. The valency of X is 2 and the valency of Z is 1. So the formula of compound is Z₂X.

c) Y is also non-metal and we know Z is metal. The valency of Y is 1. So the compound formed is ZY.

Resonance energy is defined as the difference in energy of the most stable contributing structure and the resonating forms.

1. Low ionisation enthalpy of metal atoms.

2. High electron gain enthalpy of non-metal atoms.

3. High lattice enthalpy of compound formed.

O₂ → O₂⁺ + e^-

O₂ = (16e^-) is KK (σ_2s)²(σ*_2s)²(σ_2pz)²(π_2px)²

= (π_2py)²(π*_2px)¹(π*_2py)¹

Bond order = \(\frac{1}{2}\)(10 - 6) = \(\frac{4}{2}\) = 2

O₂⁺ = (15e^-) KK (σ_2s)²( σ*_2s)²( σ_2pz)²(π_2px)²

= (π_2py)²(π*_2px)¹

Bond order = \(\frac{1}{2}\)(10 - 5) = \(\frac{5}{2}\) = 2.5

Thus, bond order of O₂ which is 2, increases to 2.5 in \(O_2^+\).

1) The process of removal of electron (s) from an atom or molecule is termed as ionisation. 

Eg : Na → Na⁺ + e^-

2) Dissociation of an ionic solid into constituent ions upon its dissolution in a suitable solvent, is also called ionisation.

Eg : NaCl_(aq) → Na⁺_(aq) Cl^-_(aq)

Formal charge on carbon

= N_v - \(\Big[N_l+\frac{N_b}{2}\Big]\) = 4 - \(\Big[0+\frac{8}{2}\Big]\)= 4 - 4 = 0

Formal charge on oxygen

= N_v -\(\Big[N_l+\frac{N_b}{2}\Big]\) = 6 - \(\Big[4+\frac{4}{2}\Big]\)= 6 - 6 = 0

The mutual sharing of one or more pair of electrons between two combining atoms results in the formation of a chemical bond called a covalent bond.

MgCl₂ is an ionic compound. Thus it can easily dissolve in polar solvents like water (like dissolves like). On the other hand it does not dissolve in a non-polar solvent like acetone.

Methane (CH₄ ) is a non-polar covalent compound. Thus it does not dissolve in polar solvents like water. On the other hand, it can easily dissolves in non-polar solvents like acetone.