Chapter 6 Chemical Bonding Why do elements combine? atoms like to have full valence shells.

3 Types of Bonds 1. Ionic 2. Covalent 3. Metallic

Electronegativity and bonding Ionic Bonding If the difference in electronegativity is more than 1.7 then the bond is ionic. Covalent Bonding 1. Polar If the difference in electronegativity is .3-1.7 then the bond is considered Polar Covalent 2. Nonpolar If the difference in electronegativity is 0-.3 then the bond is non-polar covalent

IONIC BONDS Results from the attraction between (+) and (-) ions. Metal and Non-Metal Metals lose –e to form a positive ion They will lose enough to get to the full shell underneath. Non-metals gain –e forming a negative ion. They will gain enough to get to a full outer shell. The electrons involved are the valence electrons (+) & (-) ions are attracted to each other so that the charges balance Formula Unit-A formula that shows the least amount of each ion you must have in order for the charges to balance

Physical Properties of Ionic Compounds Most are solids in the form of salts Crystalline Lattice Hard but Brittle Conduct electricity in the molten state or in a solution. Soluble in water Very strong bond High melting points

Hydrogen Carbonate (Bicarbonate) Polyatomic Ions A charged group of covalently bonded atoms Write the Formula Unit for an ionic compound with K and SO4-2 Al and NO2-1 Na and OH-1 Ca and PO43- Note that the whole “group” of atoms has a charge. Ammonium NH4+ Chlorate ClO32- Hydrogen Carbonate (Bicarbonate) HCO3- Chromate CrO42- Hydroxide OH- Sulfate SO42- Nitrate NO3- Sulfite SO32- Nitrite NO2- Phosphate PO43- Perchlorate ClO4- Carbonate CO32-

Practice Formation of ionic compounds http://www.learner.org/interactives/periodi c/groups_interactive.html

Covalent Bonds Between Non-Metal and Non-Metal Valence Electrons are shared between atoms Covalent Compounds are Represented by a molecular formula-Shows all the elements in the compound H2O C2H6O4 Lower melting and boiling points than ionic compounds

How are bonds represented? Electron Dot Notation is used to make Lewis Structures Lewis Structures A pair of electrons is represented by a dash …………. H Cl -----> H-Cl Pairs of electrons that are not bonded are called an unshared pair of electrons.

Tips for Drawing Lewis Structures Hydrogen and the halogens will never be a central atom. Why? They can only form one bond If the compound contains carbon then it will be in the middle. If no carbon then the least electronegative element will be in the middle. Why? Because these elements can form more than one covalent bond. The overall goal is to make each central atom have an octet of electrons a)CH4 b)C2H6 c)NH3 d)SiF4

Multiple Covalent Bonds If you cannot satisfy the octet rule with a single bond, try a double or triple bond. Double (two atoms share two pairs of electrons) Triple (two atoms share three pairs of electrons) Usually involve carbon, nitrogen, and oxygen.

Polar Covalent Bonds Occurs between two different nonmetal elements Examples: carbon and oxygen hydrogen and oxygen hydrogen and chlorine

Polar Covalent bonds continued Polar bonds result due to an unequal sharing of the electron pair. A pole is created due to one of the bonded atoms having a higher electronegativity. Also when there are unshared pairs of electrons Let’s draw the pole that is created by the following pairs of atoms carbon and oxygen hydrogen and oxygen hydrogen and chlorine HCl

Non Polar Covalent Bonds Result from an equal sharing of the electron pair. Mostly occur between like atoms

Non Polar Covalent Bonds Diatomic Molecules are molecules that contain the same element Seven common diatomic molecules Iodine I2 Hydrogen H2 Chlorine Cl2 Fluorine F2 Nitrogen N2 Bromine Br2 Oxygen O2

Non-Polar Covalent Cont A bond is also called non polar if the molecule is symmetrical. H : C ::: C : H

Intermolecular Forces or Vander waAls Forces Forces or attractions between molecules Much Weaker than bonds that join atoms (so much weaker than covalent bonds or ionic bonds)

1. London Dispersion Forces Occurs in all atoms and molecules Due to the constant motion of electrons Increase with increasing mass of atoms Helium Gas

2. Dipole-Dipole Acts between polar molecules H-bonds are represented by dotted lines or dashes Partial Charges of polar molecules attract one another

3. Hydrogen Bonding A type of Dipole-Dipole Force Strongest of intermolecular forces Occurs between a hydrogen that is covalently bonded to a F, O,or N and an unshared pair of electrons on another molecule.

http://www.onlinemathlearning.com/interm olecular-forces.html

Are there different types? If so what are the types? Properties Covalent Bonds Ionic Bonds How does it form? Hint: what happens with the electrons?   Are there different types? If so what are the types? Does it have a definite Shape? Melting point? High or low What is it?Define it. Boiling point? High or Low Examples: Occurs between what type of atoms? State at room temperature?

How does it form? Hint: what happens with the electrons? Properties Covalent Bonds Ionic Bonds How does it form? Hint: what happens with the electrons? A covalent bond is formed between two non-metals that have similar electronegativities. Neither atom is "strong" enough to attract electrons from the other. To help each out, they share their Valence electrons An ionic bond is formed between a metal and a non-metal. Non-metals take electrons from the metals. Non-metals form a negative ion and Metals form a positive ion. These two opposite ions attract each other and form the ionic bond. Are there different types? If so what are the types? Yes, Polar covalent and non-polar covalent No different types Does it have a definite Shape? Definite shape bonds cannot shift Crystalline Lattice Structure-can shift and reform bonds Melting point? High or low low High What is it? Define it. Covalent bonding is a form of chemical bonding between two non metal atoms. They share pairs of electrons. Ionic bond is a type of bond formed from the attraction between oppositely charged ions in a chemical compound. These kinds of bonds occur between a metal and a non metal atom. Boiling point? High or Low Low Examples: Methane (CH4), HydroChloric acid (HCl), Water (H2O) Sodium chloride-Table Salt (NaCl) Occurs between what type of atoms? Two non-metals One metal and one non-metal State at room temperature? Gaseous, Liquid, or brittle solid Solid

Metallic bonding http://www.onlinemathlearning.com/metallic- bond.html

Vocabulary for Ionic bonding Anion Cation Ionic Compound Lattice Structure Polyatomic Ion Valence Electron Formula Unit Intramolecular Force

V: Valence S: Shell E: Electron P: Pair R: Repulsion VsepR Models VSEPR Models: a model used to predict the shape of individual molecules based on the fact that electron pairs want to get as far away from other electrons pairs as possible. V: Valence S: Shell E: Electron P: Pair R: Repulsion

Baby Research Paper: What is Orbital Hybridization? Combine the concepts of hybrid orbitals and VSEPR Models to describe the shapes and structures of some common molecules. Draw Pictures and give examples Be sure to include information about sp, sp2, and sp3 2 pages (no more than ½ page should be taken up with pictures) 1 in Margins 12 in font (Times New Roman) Cover Page w/ Title, Name, Block, Date Due Monday 21st