CLASS 11 chemistry ch 4
CHEMICAL BONDING AND MOLECULAR STRUCTURE Chapter 4
CLASS 11 chapter 4
OCTET RULE
During a chemical reaction the atoms tend to adjust their electronic arrangement in such a way that they achieve 8 e- in their outermost electron. This is called octet rule.
CHEMICAL BOND
the chemical force which keeps the atoms in any molecule together is called a chemical bond.
IONIC BOND
The columbic force of attraction which holds the appositively 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.
LATTICE ENTHALPY
The molar enthalpy change accompanying the complete separation of the constituent particles that compose of the solids (such as ions for ionic solid, molecules for molecular solids) under standard conditions is called lattice enthalpy (∆lHo). The lattice enthalpy is a positive quantity.
ELECTRO VALENCY
The number of electrons lost or gain by an atom of an element is called as electrovalency.The element which give up electrons to form positive ions are said to have positive valency, while the elements which accept electrons to form negative ions are said to have negative valency.
FORMATION OF AN IONIC BOND
It is favoured by
(i) the low ionisation enthalpy of a metallic element which forms the cations,
(ii) High electron gain enthalpy of non- metallic element which forms the anions,
(iii) Large lattice enthalpy i.e; the smaller size and the higher charge of the atoms.
COVALENCY
The number of electrons which an atom contributes towards mutual sharing during the formation of a chemical bond called its covalency in that compound.
SINGLE COVALENT BOND
A covalent bond formed by the mutual sharing of one pair of electrons is called a single covalent bond, or simply a single bond. A single covalent bond is represented by a small line (−) between the two atoms.
DOUBLE COVALENT BOND
A covalent bond formed by the mutual sharing of two pair of electrons is called a double covalent bond, or simply a double bond. A double covalent bond is represented by two small horizontal lines (=) between the two atoms. E.g. O=O, O=C=O etc.
TRIPLE COVALENT 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.
FORMATION OF A COVALENT BOND
Formation of a covalent bond is favoured by
(i) High ionisation enthalpy of the combining elements.
(ii) Nearly equal electron gain enthalpy and equal electro-negativities of combining elements.
(iii) High nuclear charge and small atomic size of the combining elements.
POLAR COVALENT BOND
The bond between two unlike atoms which differ in their affinities for electrons is said to be polar covalent bond. E.g. H-Cl
COORDINATE BOND
The bond formed when one sided sharing of electrons take place is called a coordinate bond. Such a bond is also known as dative bond. It is represented by an arrow (→) pointing towards the acceptor atom. E.g. H3N→BF3
Bond Length : Bond length is defined as the equilibrium distance between the nuclei of two bonded atoms in a molecule
Bond Angle : It is defined as the angle between the orbitals containing bonding electron pairs around the central atom in a molecule/complex ion
Bond Enthalpy : 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.
Bond Order : In the Lewis description of covalent bond, the Bond Order is given by the number of ondsetween the two atoms in a molecule
Resonance : whenever a single Lewis structure cannot describe a molecule accurately, a number of tructures with similar energy, positions of nuclei, bonding and non-bonding pairs of electrons are taken as he canonical structures of the hybrid which describes the molecule accurately
Dipole moment : The product of the magnitude of the charge and the distance between the centres of positive It is the number of vectors represented by an arrow with its tail in a positive position and a head to the negative center. Diploma moment (μ) = charge (Q) x distance from division (r)
Sigma Bond. The covalent bond formed by the interference of the orbits of the two atoms along the line connecting the two atoms (orbital axis) is called the sigma bond (σ). For example, bonds formed as a result of the interference of s-s with: s-p, p-p along the orbits are sigma bonds.
PI BOND:
The covalent bond formed by the lateral interference of the p or d atoms of the two atoms is called the pi (π) bond. For example, the bond formed by the orbital coincidence of p is the bond of p.
Insects:
The connection of one molecule to the hydrogen atom
A more electronegative component of the same or another molecule is called a hydrogen bond.
hybridization
The process of mixing atomic orbits to form new hybrid orbits is called hybridization. All hybrid orbits of a certain type have equal energy, symmetrical and correspondingly oriented. Hybrid orbits are designed according to the type and atomic orbits that merge, e.g.
CLASS 11 chapter 4
OCTET RULE
During a chemical reaction the atoms tend to adjust their electronic arrangement in such a way that they achieve 8 e- in their outermost electron. This is called octet rule.
CHEMICAL BOND
the chemical force which keeps the atoms in any molecule together is called a chemical bond.
IONIC BOND
The columbic force of attraction which holds the appositively 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.
LATTICE ENTHALPY
The molar enthalpy change accompanying the complete separation of the constituent particles that compose of the solids (such as ions for ionic solid, molecules for molecular solids) under standard conditions is called lattice enthalpy (∆lHo). The lattice enthalpy is a positive quantity.
ELECTRO VALENCY
The number of electrons lost or gain by an atom of an element is called as electrovalency.The element which give up electrons to form positive ions are said to have positive valency, while the elements which accept electrons to form negative ions are said to have negative valency.
FORMATION OF AN IONIC BOND
It is favoured by
(i) the low ionisation enthalpy of a metallic element which forms the cations,
(ii) High electron gain enthalpy of non- metallic element which forms the anions,
(iii) Large lattice enthalpy i.e; the smaller size and the higher charge of the atoms.
COVALENCY
The number of electrons which an atom contributes towards mutual sharing during the formation of a chemical bond called its covalency in that compound.
SINGLE COVALENT BOND
A covalent bond formed by the mutual sharing of one pair of electrons is called a single covalent bond, or simply a single bond. A single covalent bond is represented by a small line (−) between the two atoms.
DOUBLE COVALENT BOND
A covalent bond formed by the mutual sharing of two pair of electrons is called a double covalent bond, or simply a double bond. A double covalent bond is represented by two small horizontal lines (=) between the two atoms. E.g. O=O, O=C=O etc.
TRIPLE COVALENT 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.
FORMATION OF A COVALENT BOND
Formation of a covalent bond is favoured by
(i) High ionisation enthalpy of the combining elements.
(ii) Nearly equal electron gain enthalpy and equal electro-negativities of combining elements.
(iii) High nuclear charge and small atomic size of the combining elements.
POLAR COVALENT BOND
The bond between two unlike atoms which differ in their affinities for electrons is said to be polar covalent bond. E.g. H-Cl
COORDINATE BOND
The bond formed when one sided sharing of electrons take place is called a coordinate bond. Such a bond is also known as dative bond. It is represented by an arrow (→) pointing towards the acceptor atom. E.g. H3N→BF3
Bond Length : Bond length is defined as the equilibrium distance between the nuclei of two bonded atoms in a molecule
Bond Angle : It is defined as the angle between the orbitals containing bonding electron pairs around the central atom in a molecule/complex ion
Bond Enthalpy : 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.
Bond Order : In the Lewis description of covalent bond, the Bond Order is given by the number of ondsetween the two atoms in a molecule
Resonance : whenever a single Lewis structure cannot describe a molecule accurately, a number of tructures with similar energy, positions of nuclei, bonding and non-bonding pairs of electrons are taken as he canonical structures of the hybrid which describes the molecule accurately
Dipole moment : The product of the magnitude of the charge and the distance between the centres of positive It is the number of vectors represented by an arrow with its tail in a positive position and a head to the negative center. Diploma moment (μ) = charge (Q) x distance from division (r)
Sigma Bond. The covalent bond formed by the interference of the orbits of the two atoms along the line connecting the two atoms (orbital axis) is called the sigma bond (σ). For example, bonds formed as a result of the interference of s-s with: s-p, p-p along the orbits are sigma bonds.
PI BOND:
The covalent bond formed by the lateral interference of the p or d atoms of the two atoms is called the pi (π) bond. For example, the bond formed by the orbital coincidence of p is the bond of p.
Insects:
The connection of one molecule to the hydrogen atom
A more electronegative component of the same or another molecule is called a hydrogen bond.
hybridization
The process of mixing atomic orbits to form new hybrid orbits is called hybridization. All hybrid orbits of a certain type have equal energy, symmetrical and correspondingly oriented. Hybrid orbits are designed according to the type and atomic orbits that merge, e.g.
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