The Nature of Covalent Bonding

Transcription

1 Chemistry 1 of 50 The colors in this map indicate the concentrations of ozone in various parts of Earth s atmosphere. Oxygen atoms can join in pairs to form the oxygen you breathe and can also join in groups of three oxygen atoms to form ozone. 2 of 50 1

2 > The Octet Rule in The Octet Rule in What is the result of electron sharing in covalent bonds? 3 of 50 > The Octet Rule in In covalent bonds, electron sharing usually occurs so that atoms attain the electron configurations of noble gases. 4 of 50 2

3 > Single Covalent Bonds Single Covalent Bonds How do electron dot structures represent shared electrons? 5 of 50 > Single Covalent Bonds Two atoms held together by sharing a pair of electrons are joined by a single covalent bond. 6 of 50 3

4 > Single Covalent Bonds An electron dot structure such as H:H represents the shared pair of electrons of the covalent bond by two dots. A structural formula represents the covalent bonds by dashes and shows the arrangement of covalently bonded atoms. 7 of 50 > Single Covalent Bonds The halogens form single covalent bonds in their diatomic molecules. Fluorine is one example. 8 of 50 4

5 > Single Covalent Bonds A pair of valence electrons that is not shared between atoms is called an unshared pair, also known as a lone pair or a nonbonding pair. 9 of 50 > Single Covalent Bonds The hydrogen and oxygen atoms attain noblegas configurations by sharing electrons. 10 of 50 5

6 > Single Covalent Bonds The ammonia molecule has one unshared pair of electrons. 11 of 50 > Single Covalent Bonds Methane has no unshared pairs of electrons. 12 of 50 6

7 8.1 Section Assessment 13 of 50 Section Assessment 14 of 50 7

8 8.1 Section Assessment 15 of 50 Practice Problems for Conceptual Problem 8.1 Section Assessment Problem Solving 8.8 Solve Problem 8 with the help of an interactive guided tutorial. 16 of 50 8

9 > Double and Triple Covalent Bonds Double and Triple Covalent Bonds How do atoms form double or triple covalent bonds? 17 of 50 > Double and Triple Covalent Bonds Atoms form double or triple covalent bonds if they can attain a noble gas structure by sharing two pairs or three pairs of electrons. 18 of 50 9

10 > Double and Triple Covalent Bonds A bond that involves two shared pairs of electrons is a double covalent bond. A bond formed by sharing three pairs of electrons is a triple covalent bond. 19 of 50 > Covalent Bonds Simulation 6 Simulate the covalent bonding between molecules 20 of 50 10

11 > Double and Triple Covalent Bonds Each nitrogen atom has one unshared pair of electrons. 21 of 50 > Double and Triple Covalent Bonds 22 of 50 11

12 > Double and Triple Covalent Bonds Carbon dioxide gas is soluble in water and is used to carbonate many beverages. A carbon dioxide molecule has two carbon-oxygen double bonds. 23 of 50 > Double and Triple Covalent Bonds Carbon dioxide is an example of a triatomic molecule. 24 of 50 12

13 > Coordinate Covalent Bonds Coordinate Covalent Bonds How are coordinate covalent bonds different from other covalent bonds? 25 of 50 > Coordinate Covalent Bonds In carbon monoxide, oxygen has a stable configuration but the carbon does not. 26 of 50 13

14 > Coordinate Covalent Bonds As shown below, the dilemma is solved if the oxygen donates one of its unshared pairs of electrons for bonding. 27 of 50 > Coordinate Covalent Bonds A coordinate covalent bond is a covalent bond in which one atom contributes both bonding electrons. In a structural formula, you can show coordinate covalent bonds as arrows that point from the atom donating the pair of electrons to the atom receiving them. 28 of 50 14

15 > Coordinate Covalent Bonds In a coordinate covalent bond, the shared electron pair comes from one of the bonding atoms. 29 of 50 > Coordinate Covalent Bonds A polyatomic ion, such as NH 4+, is a tightly bound group of atoms that has a positive or negative charge and behaves as a unit. Most plants need nitrogen that is already combined in a compound to grow. 30 of 50 15

16 > Coordinate Covalent Bonds 31 of 50 Section Assessment 32 of 50 16

17 Section Assessment 33 of 50 The image cannot be displayed. Your computer may not have enough memory to open the image, or the image may have been corrupted. Restart your computer, and then open the file again. If the red x still appears, you may have to delete the image and then insert it again. Section Assessment 34 of 50 17

18 Practice Problems for Conceptual Problem Section Assessment Problem-Solving 8.10 Solve Problem 10 with the help of an interactive guided tutorial. 35 of 50 > Bond Dissociation Energies Bond Dissociation Energies How is the strength of a covalent bond related to its bond dissociation energy? 36 of 50 18

19 > Bond Dissociation Energies The energy required to break the bond between two covalently bonded atoms is known as the bond dissociation energy. A large bond dissociation energy corresponds to a strong covalent bond. 37 of 50 > Resonance Resonance How are oxygen atoms bonded in ozone? 38 of 50 19

20 > Resonance Ozone in the upper atmosphere blocks harmful ultraviolet radiation from the sun. At lower elevations, it contributes to smog. 39 of 50 > Resonance The actual bonding of oxygen atoms in ozone is a hybrid, or mixture, of the extremes represented by the resonance forms. 40 of 50 20

21 > Resonance A resonance structure is a structure that occurs when it is possible to draw two or more valid electron dot structures that have the same number of electron pairs for a molecule or ion. 41 of 50 > Exceptions to the Octet Rule Exceptions to the Octet Rule What are some exceptions to the rule? 42 of 50 21

22 > Exceptions to the Octet Rule The octet rule cannot be satisfied in molecules whose total number of valence electrons is an odd number. There are also molecules in which an atom has fewer, or more, than a complete octet of valence electrons. 43 of 50 > Exceptions to the Octet Rule Two electron dot structures can be drawn for the NO 2 molecule. 44 of 50 22

23 > Exceptions to the Octet Rule NO 2 is produced naturally by lightning strikes. 45 of 50 > Exceptions to the Octet Rule The electron dot structure for PCl 5 can be written so that phosphorus has ten valence electrons. 46 of 50 23