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Unformatted text preview: Chapter 1 Structure and Bonding ; Acid and Bases 1. Basic Characteristic of organic compounds is that it all contain element carbon 2. Organic chemistry is the study of compounds of carbon 3. Special properties of carbon that enable to form the backbone of organic compounds a. It is a group 4A element which means it can share four valence electrons and form four strong covalent bond b. Carbon atoms can bond to one another forming long chains and rings c. Of all elements, carbon can form immense diversity of compounds just by combining it with hydrogen, oxygen and nitrogen. 1.1 Atomic Structure 1) Atoms consist of dense, positively charged nucleus surrounded at relatively large distance by negatively charged electrons a) Nucleus consists of subatomic particles; neutrons (electrically neutral ) and protons (positively charged). Nucleus contributes to most of the atomic mass although it is extremely small about 10-14 to 10-15 b) Electrons have negligible mass and orbits the nucleus at distance up to approximately 10-10 and thus the diameter of a typical atom is about 2*10-10 m or 200 picometers ( pm). 2) An atom is described by two numbers a) Atomic number: number of protons in nucleus b) Atomic mass : number of protons + number of neutrons 3) All the atoms of same elements have same atomic number but can have different atomic mass. a) Isotopes: Atoms of same element that have the same number of proton but different number of neutrons. In other words, atoms with same atomic number but different atomic mass/mass number. b) Isotopes have very similar chemical properties 4) Atomic weight is average mass in atomic mass units of atom of an element. 5) Distribution of electrons in an atom a) By quantum mechanical model, behaviour or specific electron in an atom can be described by wave equation. The solution to wave equation is called wave function or orbital denoted by (psi). b) Orbital can be thought as a region of space around nucleus where electrons can most likely be found. c) Orbitals are organized into different layers or shells of successively larger size and energy. Different shells contain different number and kinds of orbitals. Each orbital can be occupied by 2 electrons. 1 s orbital, 3 p orbitals, 5 d orbitals and so on. 1 st shell contains only 1 s orbital, 2 nd shell contains 1 s and 3 p orbitals. 3 rd shell contains 1s, 3p and 5d orbitals. d) Orbitals have shape. There are four different orbital shapes denoted by s, p, d, f i) The s orbital is spherical with nucleus at the centre ii) The p orbital has dumbbell shape. The three different p orbitals within a given shell are oriented in space along mutually perpendicular line. iii) The 4 of 5 d orbitals are clover shaped. 3 or them oriented on xy, yz and xz plane and one is oriented along x,y axis. The centre of all lies in a plane between a pair of axis. The fifth d orbital is dumbbell shape with a torus....
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