Question? Leave a message!




Chemical Bonding

Chemical Bonding
Dr.SamuelHunt Profile Pic
Dr.SamuelHunt,United Arab Emirates,Teacher
Published Date:21-07-2017
Website URL
Comment
Chapter 10 Chemical BondingThe two teams are joined together because both are holding onto the same rope. In a similar way, two atoms are bonded together when both hold onto the same electrons. A covalent bond is a bond formed when atoms share electrons. www.ThesisScientist.comBonding Theories • Central theme in chemistry: How and Why atoms attach together • This will help us understand how to: 1. Predict the shapes of molecules. 2. Predict properties of substances. 3. Design and build molecules with particular sets of chemical and physical properties. www.ThesisScientist.comLewis Bonding Theory • Built on the idea of valence electrons. • Atoms share there valence electrons. • Gives atoms stablity. www.ThesisScientist.comLewis Symbols of Atoms • Uses symbol of element to represent nucleus and inner electrons. • Uses dots around the symbol to represent valence electrons.  Puts one electron on each side first, then pair. • Remember that elements in the same group have the same number of valence electrons; therefore, their Lewis dot symbols will look alike. • •• •• •• •• Li• Be• •B• •C• •N• •O: :F: :Ne: • • • • • • •• www.ThesisScientist.comPractice—Write the Lewis Symbol for Arsenic, Continued. • As is in group 15, therefore it has 5 valence electrons.   As  www.ThesisScientist.comLewis Bonding Theory • Atoms ONLY come together for a single reason: • to produce a more stable electron configuration. • Atoms bond together by either transferring or sharing electrons. • A lot of atoms like to have 8 electrons in their outer shell.  Octet rule.  There are some exceptions to this rule—the key to remember is to try to get an electron configuration like a noble gas. Li and Be try to achieve the He electron arrangement. www.ThesisScientist.comLewis Symbols of Ions • Cations have Lewis symbols without valence electrons. Lost in the cation formation. They now have a full ―outer‖ shell that was the previous second highest energy shell. • Anions have Lewis symbols with 8 valence electrons. Electrons gained in the formation of the anion. •• •• +− Li• Li :F: :F: • •• www.ThesisScientist.comPractice—Show How the Electrons Are Transferred and the Bond Is Formed When Na Reacts with S. www.ThesisScientist.comPractice—Show How the Electrons Are Transferred and the Bond Is Formed When Na Reacts with S, Continued.  - 2 Na  2 Na  2 e 2-   -  S  2 e  S      www.ThesisScientist.comIonic Bonds • Metal to nonmetal. • Metal loses electrons to form cation. • Nonmetal gains electrons to form anion. • Ionic bond results from + to − attraction. Larger charge = stronger attraction. Smaller ion = stronger attraction. • Lewis theory allows us to predict the correct formulas of ionic compounds. www.ThesisScientist.comExample 10.3—Using Lewis Theory to Predict Chemical Formulas of Ionic Compounds Predict the formula of the compound that forms between calcium and chlorine. Ca Cl ∙ ∙ Draw the Lewis dot symbols ∙ ∙ ∙ of the elements. Transfer all the valance electrons Ca Cl Cl ∙ ∙ ∙ ∙ ∙ ∙ ∙ from the metal to the nonmetal, ∙           adding more of each atom as you 2+     Ca : Cl : : Cl : go, until all electrons are lost             from the metal atoms and all nonmetal atoms have 8 electrons. CaCl 2 www.ThesisScientist.com ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙ ∙Practice—Use Lewis Symbols to Predict the Formula of an Ionic Compound Made from Reacting a Metal, M, that Has 2 Valence Electrons with a Nonmetal, X, that Has 5 Valence Electrons. www.ThesisScientist.comPractice—Use Lewis Symbols to Predict the Formula of an Ionic Compound Made from Reacting a Metal, M, that Has 2 Valence Electrons with a Nonmetal, X, that Has 5 Valence Electrons, Continued.   X M   M     X M  M X 3 2  www.ThesisScientist.comCovalent Bonds • Often found between two nonmetals. • Typical of molecular species. • Atoms bonded together to form molecules.  Strong attraction. • Atoms share pairs of electrons to attain octets. • Molecules generally weakly attracted to each other.  Observed physical properties of molecular substance due to these attractions. www.ThesisScientist.comUsing Lewis Atomic Structures to Predict Bonding Between Nonmetal Atoms • Nonmetal atoms often bond to achieve an octet of valence electrons by sharing electrons. Though there are many exceptions to the Octet rule. • In Lewis theory, atoms share electrons to complete their octet. • This may involve sharing electrons with multiple atoms or sharing multiple pairs of electrons with the same atom. www.ThesisScientist.com•• • •• •• Single Covalent Bonds • Two atoms share one pair of electrons.  2 electrons. • One atom may have more than one single bond. •• •• •• F • • F H H O • • • •• •• •• •• •• •• F F H H O •• •• •• F F www.ThesisScientist.com •• •• •• ••• • Double Covalent Bond • Two atoms sharing two pairs of electrons. 4 electrons. • Shorter and stronger than single bond. •• •• O O • • •• •• •• O O •• O O www.ThesisScientist.com• • Triple Covalent Bond • Two atoms sharing 3 pairs of electrons. 6 electrons. • Shorter and stronger than single or double bond. •• •• N N • • • • •• N N •• •• N N www.ThesisScientist.comBonding and Lone Pair Electrons • Electrons that are shared by atoms are called bonding pairs. • Electrons that are not shared by atoms but belong to a particular atom are called lone pairs. Also known as nonbonding pairs. •• •• •• • •• • • Bonding pairs Lone pairs O S O • •• • • •• www.ThesisScientist.com