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Lewis Structures and Chemical Bonds Chapter 7 Suggested HW 7.1, 7.3, 7.7, 7.15, 7.17, 7.23, 7.31, 7.37, 7.39, 7.59, 7.61, 7.63, 7.67, 7.69, 7.73, 7.75,

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Presentation on theme: "Lewis Structures and Chemical Bonds Chapter 7 Suggested HW 7.1, 7.3, 7.7, 7.15, 7.17, 7.23, 7.31, 7.37, 7.39, 7.59, 7.61, 7.63, 7.67, 7.69, 7.73, 7.75,"— Presentation transcript:

1 Lewis Structures and Chemical Bonds Chapter 7 Suggested HW 7.1, 7.3, 7.7, 7.15, 7.17, 7.23, 7.31, 7.37, 7.39, 7.59, 7.61, 7.63, 7.67, 7.69, 7.73, 7.75, 7.77, 7.81, 7.97, 7.99, 7.101, 7.105, 7.107, 7.109, 7.111, 7.115, 7.119, 7.121, 7.125, 7.127, 7.129, 7.139, 7.143, 7.145, Lecture 4 1

2 Electrons dictate the chemistry of an atom Electrons fill orbitals in order or increasing energy 1s  2s  2p  3s  3p  4s  3d  4p  5s  4d  5p … We can represent the electron configuration of an element by showing the orbital designation or orbital configuration Review 2 1s 2 2s 2 2p 6 3s 2 3p 4 [Ne]3s 2 3p 4 1s11s1 Shell subshell Number of electron in subshell S 

3 Octet Rule and Ions 3 An ion is an atom that has gained or lost electrons –This results in a net charge on the atom If an ion has a net (+) charge  cation If an ion has a net (-) charge  anion Ions tend to form such that they satisfy the Octet Rule The Octet Rule – Atoms prefer to have 8 electrons in their outer shell (or dublet for H and He). Valence electrons = outer shell

4 Forming Ions 4 Na  (Z = 11)  [Ne] 3s 1 Noble gas configuration ALWAYS satisfy the octet rule Mg  (Z = 12)  [Ne] 3s 2 Cl  (Z = 17)  [Ne] 3s 2 3p 5 S  (Z = 17)  [Ne] 3s 2 3p 4

5 Lewis Representation 5 American chemist G.N. Lewis had a profound impact on our understanding of chemical bonding. One of his many contributions was a simple way to represent chemical bonds. We call these Lewis Symbols. –Valence Electrons are represented by dots. –A single dot represents an electron –A pair of dots represents two paired electrons sharing an orbital HHeNO O 2- KMg 2+ I - 1s 1 1s 2 2s 2 2p 3 2s 2 2p 4 2s 2 2p 6 3s 1 [Ne]5s 2 5p 6

6 Compound 6 Compounds Organic Compound Inorganic Compound Contains Carbon Composed of Charged components CationsAnions Covalent Ionic Bonds Bond Type

7 Electronegativity 7 Some atoms attract electrons more than others Electronegativity difference  2 Ionic Bond < 2 Covalent X-Y

8 Electronegativity 8 Predict the type of bond that will form between: Ca and F C and F B and H

9 Ionic Bonds 9 IonNa + Cl - Electron Configuration [Ne] [Ne]2s 2 2p 6 Lewis Symbol Ionic bonds do not share electrons – bond forms through charge attraction NaCl CaCl 2 IonCa 2+ Cl - Electron Configuration [Ar] [Ne]2s 2 2p 6 Lewis Symbol

10 Covalent Bonds 10 Covalent bonds  electrons shared between two atoms. This involves an overlap of atomic orbitals Let’s consider H 2 - two hydrogen atoms share electrons. H Commonly represented as: Solid line represents covalent bond Octet Rule NOT satisfied! Electrons pair and are shared between both atoms

11 Covalent Bonding 11 Energy 1s 1 Hydrogen Energy 1s 1 Hydrogen  bond

12 Covalent Bonding – Fluorine (F 2 ) 12 Energy 2s 2 Fluorine Energy 2s 2 Fluorine Atomic Orbitals are NOT optimized for bonding 2p 5 sp 3

13 Covalent Bonding 13 Energy sp 3 Energy sp 3  bond Fluorine

14 Covalent Bonding 14

15 Covalent Bonding – CH 4 15 CarbonHydrogen (x4) 1s 1 2s 2 2p 2 sp 3

16 Covalent Bonding – CH 4 16 CarbonHydrogen (x4) 1s 1 sp 3

17 Covalent Bonding – CH 4 17 CarbonHydrogen (x4) 1s 1 sp 3

18 Covalent Bonding – CH 4 18

19 Covalent Bonding – NH 3 19

20 Covalent Bonding – NH 3 20

21 Covalent Bonding – NH 3 21

22 Covalent Bonding – NH 3 22

23 VSEPR 23 Valence Shell Electron Pair Repulsion Each region of electrons (bond or lone pair) counts as a balloon Balloons want to spread out as much as possible

24 Molecular Shapes 24

25 Molecule Polarity 25 Will each of these molecules be polar? CH 4 CH 3 F CH 2 F 2 CHF 3 CF 4


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