1. CHAPTER 5: CHEMICAL BONDING Name:Prachayanee Chueamsuwanna Date: Oct. 19,2015

2. INTRODUCTION  A chemical bond is an attraction atoms that allows the formation of chemical substances that contain two or more atoms.  Three basic types of bonds includes a. Ionic, electrostatic attraction between ions. b. Metallic, metal atoms bonded to several other atoms. c. Covalent, sharing of electrons.

3. VALENCE ELECTRONS  Valence electrons are electrons in the outermost shell of an atom; electrons in the highest occupied energy level. The number of valence electrons determines the properties of an element.  To determine the number of valence electrons, simply look at its group number. The number of valence electrons is related to its group.

4. LEWIS SYMBOLS  When forming compounds, atoms tend to share, add or subtract electrons electrons until they are surrounded by eight valence electron.  Lewis devised a system, the Lewis dot system, where dots represent the valence electrons, and are moved or combined to represent processes and bonding.  This was only applied to the s and p block elements.

5. THE OCTET RULE  The Octet rule states that atoms of metals tend to lose their valence electrons until they have configuration of noble gases with eight valence electrons and atoms of nonmetals tend to gain electrons or share electrons until they attain noble gas structure wit eight electrons in the outermost shell.

6. IONS  An ions is an atom or group of atoms that has lost or gained electrons to form a charged (positive or negative) species.  Ion form when an atom or group of atoms loses or gain electrons.  A positively charged ion called a cation is produced when an atoms loses one or more valence electrons.  A negatively charged ion is called anion and is produced when an atoms loses electrons. (name of anions end with –ide).  Halogen ions are called halides

7. IONIC BONDS AND IONIC COMPOUNDS  When electrons are transferred from one atom to another it is called ionic bonding.  An ionic bond is a type of chemical bond where one or more electrons are transferred from one atom to another.  An ionic compound is one formed between a cation and an anion. Although they are composed of ions ionic compound are electrically neutral.  Cations and anions have opposite charges and therefore attracts each other by means of electrostatic forces forming bonds called ionic bonds.

8. THE CRYSTAL LATTICE STRUCTURE OF IONIC COMPOUNDS  Ionic substances are actually a combination of lots of ions bonded together into a giant molecule. The arrangement of ions in a regular, geometric structure is called a crystal lattice.  Ionic bonds hold atoms together in the lattice structure.

9. PROPERTIES OF IONIC COMPOUNDS  Electrostatic forces hold together ionic compounds, making them hard, and high melting.  Most ionic compounds, when they do dissolve in water, do not conduct electricity.

10. METALLIC BONDING  Metallic bonding is the electrostatic attraction between the positively charged atomic nuclei of metal atoms and the delocalized electrons in the metal.  The structure of a metallic bonding is quite different from covalent and ionic bonds. In a metallic bond, the valence electrons are delocalized, meaning that an atom’s electrons do not stay around that one nucleus.  In metallic bond, the positive atomic nuclei are surrounded by a sea of delocalized electrons which are attracted to the nuclei.

11. PROPERTIES OF METALS  The physical properties of metals are the result of the delocalized of the electrons involved in metallic bonding.  The solid and liquid metals conduct heat and electricity. The delocalized electrons are free to move in the solid lattice.  Metals have high melting and boiling points because of the strength of the metallic bond.  Metals are malleable and ductile.  Metals typically have a shiny, metallic luster.

12. METALS ALLOY  An alloy is a mixture or metallic solid solutions composed of two or more elements.  Alloys are important because their properties are often superior to those of their components.  Most important alloys are steels.

13. COVALENT BONDING  Covalent bonding is a form of chemical bonding where pairs of electron are shared between atoms.  Covalent bonding occurs between the atoms of non-metals.  The outermost orbitals of the atoms overlap so that unpaired electrons in each of the bonding atoms can be shared.  By overlapping orbitals, the outer energy shells of all the bonding atoms are filled.  The shared electrons move in the orbitals around both atoms. As they move, there is an attraction between these negatively charged electrons and positively charged nuclei.  This attractive force holds the atoms together in a covalent bond.

14. SINGLE, DOUBLE, TRIPLE BONDS AND BOND LENGTH  Single bonds are where two atoms share one pair of electrons.  Double bonds when two atoms share two pairs of electrons.  Triple bonds when three pairs are shared.  Bond length are the distance between covalently bonded atoms.  Double bonds are shorter than single bonds, and triple bonds are the shortest. Multiple bonds are more stable than single bonds.

15. MOLECULES AND MOLECULAR COMPOUNDS  A molecule is comprised of atoms held together by chemical bonds.  Several elements occur naturally as diatomic molecules.  Molecular compounds are composed of different atoms bonded together by covalent bonds and almost always contain only nonmetals.  Polyatomic molecules are molecules where more than two atoms are bonded.  A molecular formula shows how many atoms of each elements a substance contain.  We use molecular models to try and visualize and represent molecules. These include space filling molecular model and ball and stick molecular model.  Structural formula shows the order in which atoms are bonded.  Perspective drawings also show the three dimensional array of atoms in a compound.

16. PROPERTIES OF COVALENT COMPOUNDS  Covalent compound have several properties that distinguish them from ionic compounds and metals.  The melting point and boiling points of covalent compounds are generally lower than those of ionic compounds.  Covalent compounds are generally more flexible than ionic compounds.  Covalent compounds generally do not conduct electricity when dissolved in water, for example plastic are covalent compounds and many plastics are water resistant.  Covalent compounds generally do not conduct electricity when dissolved in water, for example iodine dissolved in pure water does not conduct electricity.