Bonding

Electron Configuration Remember that electron configuration refers to the arrangement of electrons in the orbital of an atom!

Three Types We will study . . . Ionic Bonding Covalent Bonding Metallic Bonding occurs between a metal and a nonmetal occurs between two nonmetals occurs WITHIN a metal sample

Ionic and Covalent Bonding Video Clip http://www.youtube.com/watch?v=QqjcCvzWwww

Chemical Bonding Compounds are formed from chemically bound atoms or ions. Bonding involves only the valence electrons. When atoms combine we call them molecules.

Valence Electrons Electrons are found in specific orbits/clouds spinning around the nucleus Valence electrons are the electrons located in the outermost orbit Elements become stable when: their outer orbit contains 8 electrons or their outer orbit becomes empty Lewis Dot Diagrams show the # of Valence Electrons

The Octet Rule When the highest energy level of an atom is filled, the atom is stable. Atoms tend to gain, lose, or share electrons until they have eight valence electrons. Hydrogen and Helium are the only exceptions. Because they are so small, they are satisfied with two valence electrons. Why are the noble gases unreactive?

Complete this chart:

Lewis Symbols / Electron Dot Diagram Lewis symbols show the valence electrons as dots arranged around the atomic symbol. hydrogen: sodium: chlorine: H · Na · Cl · · ·

Lewis Dot Diagrams of Selected Elements Show the number of valence electrons Lewis Dot Diagrams of Selected Elements                                                                                                                                                       

Oxidation # An oxidation number indicates how many electrons are lost or gained during the bonding process. Mg loses 2 electrons so it has an oxidation number of +2 Oxygen gains 2 electrons so it has an oxidation number of –2.

The periodic table show the common oxidation numbers for groups on the periodic table.

= Ionic Bonds – formed when atoms gain or lose electrons. Ex: Na has 1 valence e- =

When Na loses that electron, its 2nd E.L. becomes full and stable with 8 e-. Atoms with an electrical charge are called ions.

Ionization When an atom loses or gains electrons they become ions – or atoms with an electrical charge. If an atom LOSES an electron, it becomes an ion with a +1 charge. If an atom GAINS an electron, it becomes an ion with a –1 charge.

Chlorine has 7 valence electrons. If Cl gains 1 electron, its valence shell will be full and stable.

Opposites attract, so…

Ionic Bonds Na Cl Cation Anion form between a metal and a nonmetal form as a result of a transfer of electrons Na becomes a positive ion = Cl becomes a negative ion = Cation means “to go down” – also think cast off Anion means “to go up” Also think accept Na · Cl · · Cation Anion

Ions 1. Positively or negatively charged atoms. 2 Ions 1. Positively or negatively charged atoms. 2. (Number of protons not equal to the number of electrons.) 3. Metals – give up electrons to form positive ions. (example: ) 4. Nonmetals – take in electrons to form negative ions. (example: )

Ionic Bonds What is the formula for the compound that forms between magnesium and chlorine? Cl · · · Mg · · Cl · · ·

Ionic Compounds Ionic compounds consist of a lattice of positive and negative ions.

Ionic Compounds, Characteristic Properties High melting points High boiling points Conduct electric current when melted and when dissolved in solution All of these properties are a result of the strong attraction among ions within the crystal lattice

Animated Reaction sodium and chlorine http://www.visionlearning.com/library/module_viewer.php?mid=55 Youtube video of sodium reacting with chlorine

Covalent Bonds form between two nonmetal atoms form as a result of a sharing of electrons

Covalent Bonding Most atoms share electrons to gain an octet. Covalent bonds are formed when e- are shared.

Diatomic molecules: – covalently bonded atoms of the same type. Exs: H2 Cl2 F2 I2 O2 Br2 N2

Polar Molecules The type of atoms and their shape determine if a molecule is polar or not With polar molecules there is an uneven distribution of charge…one atom has a stronger attraction for the electrons than the other Polar molecules attractions are stronger than nonpolar molecules

Polar Covalent Bonding in a water molecule http://www.visionlearning.com/library/module_viewer.php?mid=55

Molecular Compounds, Characteristic Properties Note the correct name for a compound that contains covalent bonds Low melting points Low boiling points Usually gases or liquids at room temp. Does not conduct electricity well May or may not dissolve in water (there are several types of molecular compounds)

In GENERAL: Ionic Bonds– metal / nonmetal Covalent Bonds– 2 nonmetals

Double Bubble – Compare/Contrast Ionic and Covalent Bonding

Double Bubble – Compare/Contrast Ionic and Covalent Bonding