Tiêu đề 1. CW_CHEMICAL BONDING.pdf ✅

VII -Chemistry (Vol-II) 1 Narayana Group of Schools Olympiad Class Work Book CONCEPT FLOW CHART C H E M I C A L B O N D I N G Formation of Chemical Bond Co-ordinate covalent Bond p-p Overlapping sp 3 sp d3 sp d3 2 Covalent Bond s-p Overlapping sp 2 Lewis dot Structure Ionic Bond s-s Overlapping sp σ - Bond formed Lewis Octet rule σ- Bond formed Lewis Symbol Types of Chemical Bond VBT Orbital Overlapping Hybridisation VSEPR Theory To predict the Geometry of individual molecule Bond Energy Bond Length Bond angle Bond Parameters CH4 PCl5 S 6 BCl3 BeCl2 Non polar covalent bond Polar covalent Bond σ, Π - Bond formed F
VII -Chemistry (Vol-II) 2 Narayana Group of Schools Olympiad Class Work Book Over the seven decades of his scientific career, Pauling’s research interests were amaz- ingly wide-ranging and eclectic. He made important discoveries in many different fields of chemistry — physical, structural, analytical, inorganic, and organic chemis- try, as well as biochemistry. He used theoretical physics, notably quantum theory and quantum mechanics, in his investigations of atomic and molecular structure and chemical bonding. He ventured into metallurgy and mineralogy through the study of atomic structures and bonding of metals and minerals and, with his colleagues, pub- lished the structures of hundreds of inorganic substances, including topaz and mica. In both theoretical and applied medicine he made important discoveries in genetic diseases, haematology, immunology, brain function and psychiatry, molecular evo- lution, nutritional therapy, diagnostic technology, statistical epidemiology, and bio- medicine. Linus Pauling 28 -Feb-1901 - 19 -Aug - 1994 Pauling was one of the founder of the fields of quantum chemistry and molecular biology. His contributions to the theory of the chemical bond include the concept of orbital hybridisation and the first accurate scale of electro negativities of the elements. Orbital hybridisation (or hybridization) is the concept of mixing atomic orbitals into new hybrid orbitals (with different energies, shapes, etc., than the component atomic orbitals) suitable for the pairing of electrons to form chemical bonds in valence bond theory. Hybrid orbitals are very useful in the explanation of molecular geometry and atomic bonding properties and are symmetrically disposed in space. Although sometimes taught together with the valence shell electron-pair repulsion (VSEPR) theory, valence bond and hybridisation are in fact not related to the VSEPR model
VII -Chemistry (Vol-II) 3 Narayana Group of Schools Olympiad Class Work Book CHEMICAL BONDING INTRODUCTION: Matter is made up of same or different kinds of elements. Under normal conditions, no other element exists as an independent atom in nature, except noble gases. Atoms of same or different kinds of elements combine to form molecules. Molecules are the aggregates of atoms held together by the forces of attraction, called chemical bond and behave as a single entity. Definition of Chemical Bond: “The attractive force that holds two or more atoms (or) ions together in a molecule or ion is called a chemical bond”. (or) “The Phenomenon of union of two or more atoms involving redistribution of electrons, so that each atom involved in bonding acquires stable electronic configuration in order to gain the stability is known as chemical bonding”. Explanations for the formation of chemical bond: Atoms are combining to form molecules for two reasons. They are: I) To reduce the energy: 1) Every system of the universe tends to lose potential energy and become more stable. That means every system of the universe tends to change from a higher energy state (i.e., less stable state) to lower energy state (i.e., more stable state). 1 Stability Energy  A) Nuclear Forces: Do nuclei contain attractive or repulsive forces? repulsion repulsion Proton Proton Electron Electron Proton Proton Electron Electron Electrostatic Forces Strong Nuclear Forces Attraction New attractions Attraction Example: Stretched rubber bands contract, red hot Iron radiates heat and cools down, water flows spontaneously from hills to plains.