Covalent Bonds Covalent bond is a bond formed
Covalent Bonds • Covalent bond is a bond formed when 2 electrons are shared between atoms • H + H forms H 2 • Lewis Structure of F 2 • A lone pair is any electrons not shared in a covalent bond (a. k. a nonbonding electrons)
Drawing Lewis Structures • Follow the octet rule - an atom wants to have 8 valence electrons. CH 4 H 2 O
Rules for Drawing Lewis Structures Example CCl 4 • 1. Count total number of valence electrons from all atoms plus electrons from charge of molecule –C = 4 e – 4 Cl = 4 x 7= 28 e – charge = 0 0 e – 32 total e • 2. Set the least electronegative non-H atom at the center C – C is 2. 6 – Cl is 3. 2
Rules for Drawing Lewis Structures 3. Place other atoms around it with a bond connecting each atom to the central atom (1 bond = 2 electrons) 4. Put any remaining electrons around atoms as lone • • pairs or double bonds to make octet • • C Cl • • 24 e /2 = 12 lone pairs • • Cl • • 32 total e - 8 bonding e 24 nonbonding e • • Cl
Rules for Drawing Lewis Structures • 5. Check Structure with Formal Charge – F. C. = # original electrons - #bonds - 2(# lone pairs) – F. C = 0 is best, but close to zero (+1, -1) is acceptable • • Cl • • Cl • • • • F. C. Cl = 7 original e - 1 bonds - 2(3) lone pairs Chlorine 0 good Cl • • F. C. C = 4 original e - 4 bonds - 2(0) loan pairs. Carbon 0 good • •
Rules for Drawing Lewis Structures • CO 2 • Cl. O 4 • NF 3
Group Work • Draw the Lewis structures of the following – H 2 O – PCl 3 – CS 2 – NO 3– IF 3
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