A Review of General Chemistry PDF

A Review of General Chemistry Chapter 1 Jamshed Nisar 1 A Review of General Chemistry Introduction to Organic Chemistry Organic compounds: derived from living organisms Inorganic compounds: derived from nonliving sources Vital Force Theory and its rejection The Structural Theory of Matter Subs...

A Review of General Chemistry Chapter 1 Jamshed Nisar 1 A Review of General Chemistry Introduction to Organic Chemistry Organic compounds: derived from living organisms Inorganic compounds: derived from nonliving sources Vital Force Theory and its rejection The Structural Theory of Matter Substances have specific arrangement of atoms. For example: An organic compound having molecular formula C2H6O have two different arrangement of atoms The compounds which have same molecular formula but differ in constitution are constitutional isomers Jamshed Nisar 2 A Review of General Chemistry Page 3 Organic Chemistry ,David Klein Draw all constitutional isomers that have the molecular formula C3H8O. Practice to draw constitutional isomers with the following molecular formula C3H7Cl, C4H10, C5H12, C4H10O, C3H6Cl2, C6H14, C2H5Cl, C2H4Cl2, C2H3Cl3, C2H6O, C2H6O2, C2H4Br2 Jamshed Nisar 3 A Review of General Chemistry Quantum Numbers • Quantum numbers are a set of numerical values used to describe an electron in an atom. • It is the complete address of electron. • There are a total of& 4 quantum numbers. * Principal Quantum Number (n) p = e • Represents the shell (orbit or energy level) in which electrons revolve around the nucleus. • Its values are non-zero, positive integers up to infinity. (n = 1,2,3,4,5,……..) • Letter notations K, L, M, N, etc. are also used to denote the various shell. • A shell can have a maximum of 2n2 electrons. n=1 n=2 n=3 n=4 1st orbit 2nd orbit 3rd orbit 4th orbit K Shell L Shell M Shell N Shell orbit shells = maximum of 2 electrons maximum of 8 electrons maximum of 18 electrons maximum of 32 electrons levels energy (energy Jamshed Nisar increases ( 4 A Review of General Chemistry * Azimuthal Quantum Number (l) • Its values depend upon the values of Principal quantum number (n). The values are l = 0,1,2,3,……..(n-1) * principle quantum number • The values represent different sub shells which are designated by small letters s, p, d and f. • The formula for calculating the maximum number of electrons in various sub shells is 2(2l + 1). orbit ->0 first l=0 & l=1 l=2 l=3 s sub shell p sub shell d sub shell f sub shell maximum of 2 electrons maximum of 6 electrons maximum of 10 electrons maximum of 14 electrons Jamshed Nisar 5 A Review of General Chemistry Relationship between principal and azimuthal quantum numbers n=1 K-shell (2 electrons) l=0 s sub shell 1s n=2 L-shell (8 electrons) l=0 l=1 s sub shell p sub shell 2s (2 electrons) 2p (6 electrons) n=3 M-shell (18 electrons) l=0 l=1 l=2 s sub shell p sub shell d sub shell 3s (2 electrons) 3p (6 electrons) 3d (10 electrons) n=4 N-shell (32 electrons) l l l l s sub shell p sub shell d sub shell f sub shell 4s 4p 4d 4f =0 =1 =2 =3 Jamshed Nisar (2 electrons) (2 electrons) (6 electrons) (10 electrons) (14 electrons) 6 A Review of General Chemistry * Magnetic Quantum Number (m) • Its values depend upon the values of azimuthal quantum number. m = +l 0 -l • The total values of m = (2l + 1) • Different values of ‘m’ gives information about orbitals of s, p, d or f sub shells arranged along x, y and z-axes. • Each orbital can have a maximum of 2 electrons. • Orbitals differ in shape s orbital is spherical and orbitals of p are dumb-bell shaped. Jamshed Nisar 7 A Review of General Chemistry Ll = 0 s sub shell (2 electrons) m=0 s orbital 2e •Orbitals are grouped in shells l=1 p sub shell (6 electrons) Iiiio0lllp sub shell has 3 orbitals l=2 m= +1 , 0 , -1 px py pz x 2e 2e 2e •Each shell contains different types and number of orbitals d sub shell (10 electrons) m = +2 , +1 , 0 , -1 , -2 d sub shell has 5 orbitals 2e 2e 2e 2e 2e Jamshed Nisar 8 A Review of General Chemistry * Spin Quantum Number (s) • The two electrons in the same orbital have different spins. One of the electron has clockwise spin and the other has counter clockwise spin. • Clockwise spin s = + ½ or ↑ • Counter clockwise spin s = - ½ or ↓ Jamshed Nisar 9 A Review of General Chemistry Filling Atomic Orbitals with Electrons Three principles to fill electrons 1. Aufbau Principle:The lowest energy orbital is filled first. 2. Pauli Exclusion Principle:- No two electrons of the same atom can have same four Quantum Numbers. (Each orbital can accommodate a maximum of two electrons that have opposite spin. Organic Chemistry ,David Klein Jamshed Nisar 10 A Review of General Chemistry 3. Hund’s Rule:- If degenerate (equal energy) orbitals are available the electrons will live in separate orbitals with same spin rather than live in the same orbital with paired spin. Jamshed Nisar 11 A Review of General Chemistry Jamshed Nisar 12 A Review of General Chemistry Jamshed Nisar 13 A Review of General Chemistry Jamshed Nisar 14 A Review of General Chemistry Jamshed Nisar 15 A Review of General Chemistry Jamshed Nisar 16 A Review of General Chemistry (Lewis Structure of Atoms) Jamshed Nisar 17 A Review of General Chemistry Jamshed Nisar 18 A Review of General Chemistry Jamshed Nisar 19 A Review of General Chemistry Jamshed Nisar 20 A Review of General Chemistry Jamshed Nisar 21 A Review of General Chemistry Jamshed Nisar 22 A Review of General Chemistry Write an equation for the reaction of Calcium and Florine atom: Jamshed Nisar 23 A Review of General Chemistry Jamshed Nisar 24 A Review of General Chemistry Jamshed Nisar 25 A Review of General Chemistry • Atomic Size • Nuclear Charge • Shielding Effect Jamshed Nisar 26 A Review of General Chemistry Jamshed Nisar 27 A Review of General Chemistry Jamshed Nisar 28 A Review of General Chemistry Partial Periodic Table Jamshed Nisar 29 A Review of General Chemistry Jamshed Nisar 30 A Review of General Chemistry Partial Periodic Table Jamshed Nisar 31 A Review of General Chemistry Organic Chemistry ,David Klein Jamshed Nisar 32 A Review of General Chemistry * Which atom would lose an electron more easily? Na or Mg * Which one is more electropositive? Na or K •Which atom would lose an electron more easily? Na or K Jamshed Nisar 33 A Review of General Chemistry Jamshed Nisar 34 A Review of General Chemistry Jamshed Nisar 35 A Review of General Chemistry (Lewis Structure of CH4) Jamshed Nisar 36 A Review of General Chemistry Jamshed Nisar 37 A Review of General Chemistry (Lewis Structure of C2H4) (Lewis Structure of CO2) Jamshed Nisar 38 A Review of General Chemistry (Lewis Structure of HCN) (Lewis Structure of C2H2) Practice to draw Lewis structure for each of the following compounds: C2H4, C2H2, C3H8, C2H6, C3H6, CH3OH Jamshed Nisar 39 A Review of General Chemistry ↓ dis electoreput ( Jamshed Nisar it 40 A Review of General Chemistry Jamshed Nisar 41 A Review of General Chemistry Page 9 Organic Chemistry ,David Klein Electronegativity Difference Less than 0.5 Covalent bond 0.5-1.7 Polar Covalent bond greater than 1.7 Ionic bond Example: Electronegativity Difference Example: Electronegativity Difference Example: Jamshed Nisar 42 A Review of General Chemistry Jamshed Nisar 43 A Review of General Chemistry Jamshed Nisar 44 A Review of General Chemistry Draw the structure of methyl chloride and where appropriate indicate the bond Polarity with an arrow. The molecular formula of methanal (formaldehyde) is H2CO. Draw the structure That shows how the valence electrons are arranged. Jamshed Nisar 45 A Review of General Chemistry Jamshed Nisar 46 A Review of General Chemistry Jamshed Nisar 47 A Review of General Chemistry Jamshed Nisar 48 A Review of General Chemistry (Valence Bond Theory) Jamshed Nisar 49 A Review of General Chemistry Hybridization • Hybridization is a phenomenon in which orbitals with different in energy and different in shapes combine to give orbitals which are equal in energy and similar in shapes. • Valence shell orbitals take part in hybridization • 3 types of hybridizations takes place in organic compounds (sp3 , sp2 & sp) • Alkanes (C-C) show sp3 hybridization • Alkenes (C=C) show sp2 hybridization • Alkynes (C ≡C) show sp hybridization Jamshed Nisar 50 A Review of General Chemistry sp3 Hybridization • Formed by combining one s and three p orbitals • sp3 hybrid orbitals have 25% character of s and 75% character of p (s and p in the ratio of 1:3) • Four equivalent (equal energy) sp3 hybrid orbitals are produced • The hybrid orbitals have lesser energy compared to unhybridized orbitals • Each sp3 hybrid orbital has one electron (Hund’s rule) Atomic Number of C = 6 Electronic configuration of C 1s2 , 2s2 , 2px1 , 2py1 , 2pz Jamshed Nisar 51 A Review of General Chemistry sp3 Hybridization • The new sp3 hybrid orbitals have tetrahedral geometry with carbon at the centre. • The hybrid orbitals are oriented in space around the carbon at an angle of 109.50 Jamshed Nisar 52 A Review of General Chemistry sp3 Hybridization Carbon sp3 hybrid orbitals can overlap with hybrid orbitals or non hybridized atomic orbitals Methane molecule is formed by the overlap of sp3 hybrid orbitals of carbon with 1s orbitals of four hydrogen atoms separately to form four sigma bonds Jamshed Nisar 53 A Review of General Chemistry Jamshed Nisar 54 A Review of General Chemistry In ethane molecule, the two carbons have sp3-sp3 sigma bond and six hydrogens have sp3-s sigma bonds Jamshed Nisar 55 A Review of General Chemistry sp2 Hybridization • sp2 hybrid orbitals are formed by intermixing one s and two p orbitals • One of the p orbitals remain unhybradized whose axis is perpendicular to the plane formed by the three sp2 hybrid orbitals • sp2 hybrid orbitals have 1:2 ratio of s and p • Three equivalent sp2 hybrid orbitals are formed • Each of the sp2 hybrid orbitals and unhybradized p orbital have one electron Atomic Number of C = 6 Electronic configuration of C 1s2 , 2s2 , 2px1 , 2py1 , 2pz Jamshed Nisar 56 A Review of General Chemistry • sp2 hybrid orbitals lie in a plane and are directed towards the corner of an equatorial triangle • The angle between sp2 hybrid orbitals is 1200 Jamshed Nisar 57 A Review of General Chemistry Consider the case of ethene What happens when two sp2 hybridized C’s are brought together? -sp2 sigma bond Jamshed Nisar 58 A Review of General Chemistry sp2─s sigma bond 1200 Jamshed Nisar 59 A Review of General Chemistry Rotation about a double bond is restricted For rotation to occur we would have to break the pi bond For ethylene; 62 Kcal/mole thermal energy is required to break the pi bond which is much more than is available at room temperature Jamshed Nisar 60 A Review of General Chemistry More s character in sp2 hybrid orbitals (33%) as compared to that of sp3 (25%) s orbitals are closer to nucleus which decreases the bond length Jamshed Nisar 61 A Review of General Chemistry sp Hybridization • sp hybrid orbitals are formed by intermixing one s and one p orbital • Two of the p orbitals remain unhybradized whose axis are perpendicular to the plane formed by the two sp hybrid orbitals • sp hybrid orbitals have 1:1 ratio of s and p • Two equivalent sp hybrid orbitals are formed • Each of the two sp hybrid orbitals and two unhybridized p orbital have one electron Atomic Number of C = 6 Electronic configuration of C 1s2 , 2s2 , 2px1 , 2py1 , 2pz Jamshed Nisar 62 A Review of General Chemistry sp hybrid orbitals have a linear shape with a bond angle 1800 2py 2pz Two unhybridized p orbitals Jamshed Nisar 63 A Review of General Chemistry Consider the case of ethyne sp hybrid orbital of one carbon overlaps linearly with the sp hybrid orbital of other carbon to give sp-sp sigma bond Remaining sp hybrid orbital of each carbon overlaps with s orbital of hydrogen to give sp-s sigma bond Each unhybridized p orbital on carbon overlaps with the p orbital of neighboring carbon atom in parallel fashion to give rise to a pi bond. (C≡C) : one sp-sp sigma bond b/w two carbons two pi bond b/w two carbons sp-s sigma bonds b/w carbon and hydrogen Jamshed Nisar 64 The End Jamshed Nisar 65