 Bonding: Explains why atoms stick together to form molecules or formula units  The bonding of everything is tied to the electronic structure *Remember electron configuration Mg12e - 1s 2 2s 2 2p 6 3s 2 Cl17e - 1s 2 2s 2 2p 6 3s 2 3p 5

 Having a full valence (outermost s and p orbitals) gives especially low energy, a stable configuration – lower energy is what the universe likes.  Covalent and ionic compounds are made because they are lower in energy than their individual elements; which is why compounds form and stay together (bonded).

 Atoms can achieve a full octet (valence) in two ways  -either by transferring an e- (ionic bonds)  or sharing an e- (covalent bonds)

 Ionic bonds occur between a metal and a nonmetal.  They stay together because opposite charges attract (like magnets) called electrostatic attraction.  This happens because of very different electronegativities.

 Ionic bonds are one of the strongest types of bonding.  Ionic bonds are very strong, so ionic compounds are usually hard, brittle, with very high melting points and boiling points.  Ions are packed into repeating patterns resulting in a crystal lattice structure.

 No single particle of an ionic compound → represented by the simplest ratio of ions, called a formula unit.  Ionic compounds also dissolve well in water and split up into their ions called dissociation. Because of this, ionic compounds are known as electrolytes b/c ions conduct a current when dissolved in water. Good conductors of electricity as a liquid or when dissolved in water

 Superscript = charge H 1+ O 2-  Subscript = # of atoms (do not write subscripts of 1) H 2 O 2 hydrogen atoms and 1 oxygen atom H 2 O 2 2 hydrogen atoms and 2 oxygen atoms

 If lithium and fluorine bond, Li + and F - would make LiF, because the positive 1 charge balances a negative 1 charge. LiFLi 1+ F 1-

 If lithium (Li + ) and oxygen (O -2 ) bond, more positive lithiums are needed to balance out the larger negative of oxygen. It would take 2 lithiums for every 1 oxygen. To show two lithiums are needed, a subscript of “2” is written after the lithium, Li 2 O Li OLi 1+ O 2- Li 1+ Li

 If an ionic compound is made from Aluminum (Al +3 ) and Sulfur (S -2 ), the amounts of each element needed would be: Al +3 S -2 S -2 Totals: +6 and -6 So the resulting compound would be Al 2 S 3

AlS S S -2 Al +3 S -2 Al +3 S -2

AlS AlS S S -2 Al +3 S -2 Al +3 S -2

 Calcium oxide, CaO  Potassium nitride, K 3 N  Magnesium phosphide, Mg 3 P 2

 Chemical bond that results from the sharing of valence electrons to get full octets  The great majority of covalent bonds form between nonmetals

 Groups of nonmetals combine to make units called molecules (remember, ionic compounds form formula units)  The bonds between the atoms in a molecule are strong, but the attraction between the molecules is relatively weak. These attractive forces are known as intermolecular forces, or van der Waals forces.

 Covalent compounds usually have low melting points and boiling points b/c they’re easy to split apart from each other. compounds are soft.  Examples H 2 0 melts at 0.0˚C CF 4 melts at –150˚ and boils at –129˚C

 Many covalent compounds tend to be gases and liquids at room temperature, while ionic compounds are almost always solids at 25˚C (room temp.)

 Covalent compounds do not conduct electricity  Many are polar  The only purely covalent bond is between atoms of the same element

Hydrogen and Bromine. Hydrogen has 1 valence electron, Bromine has 7. Both need 1 more electron to form a stable noble gas configuration…so they form a single covalent bond  Use Lewis dot diagrams to show electrons, and a line to show covalent bond H Br H – Br Or H Br

 Oxygen and Hydrogen HO H H – O Or H O H H

 Carbon and Chlorine: CCl Cl Cl Cl – C – Cl Cl

 Carbon and Chlorine: CCl Cl Cl OrCl C Cl Cl

 Sulfur and oxygen  Nitrogen and hydrogen

 Multiple Covalent bonds: sharing more than 1 pair of electrons between two atoms (double or triple bonds) Oxygen gas, O 2 O O O=O Or O O

 Nitrogen gas, N 2 N N N N Or N N

 Carbon dioxide, CO 2 C O O O=C=O Or O C O

 Polar bonds - a covalent bond in which the electrons are not shared equally. One atom has a greater attraction for the electrons (a greater electronegativity), so the electrons spend more time around that atom, creating a slightly negative charge. The other atom then has a slightly positive charge.  Ex. H 2 O: big difference in electronegativity for oxygen and hydrogen. Oxygen pulls the electrons most of the time creating a slightly (-) charge, leaving the hydrogen with a slightly (+) charge

IonicCovalent Formula UnitSmallest UnitMolecule Transfer Electrons How FormedShare Electron Strong BondsBond StrengthWeak Bonds Repeating Patterns Crystal Structure ShapeGeometric Shape VSEPR Model

IonicCovalent Metal To NonmetalForms Between Between Nonmetals Good Conductor When Dissolved Conduct Electricity Poor Conductors Attraction Between (+) Ion and (-) Ion Cation metals Anion nonmetal When Forming Unequal Sharing = Polar Bond Equal Sharing = Nonpolar Bond High Melting and Boiling Points, Hard, Brittle Solids PropertiesLow Melting and Boiling Points, Soft, Solids, Liquids, or Gases

 Trying to fill outer shell (valance)  Compounds are neutral overall (no charge)  Can create many different compounds  Contains more than 1 electron/atom xQ8

 In metals the electrons are delocalized, which means they do not belong to any one atom but move freely from atom to atom. These electrons form a sea of electrons around the metal atoms. Metallic bonding is the attraction between metal atoms and the surrounding sea of electrons.

 These mobile electrons can act as charge carriers in the conduction of electricity or as energy conductors in the conduction of heat, which is why solid and liquid metals conduct heat and electricity.

 Metallic bonding accounts for many physical properties of metals  Metals have high melting and boiling points because of the strength of the metallic bond

 Malleability is the ability of a solid to bend or be hammered into other shapes without breaking since the electrons can slide past each other easily.  Ductility is sustaining large permanent changes in shape without breaking b/c the atoms can slide over each other easily. Ex. A piece of metal is drawn into a wire.

 Heat conduction (or Thermal conduction) is the transfer of energy between particles in a solid. The temperature of the material measures how fast the atoms are moving and the heat measures the total amount of energy due to the vibration of the atoms.

When one part of a metal is heated, the atoms in this part vibrate faster and are more likely to hit their neighbors. When collisions take place, the energy is passed on to the neighboring atoms allowing the energy to travel through the solid.

1. the number of electrons in the delocalized 'sea' of electrons. (More delocalized electrons results in a stronger bond and a higher melting point.) 2. packing arrangement of the metal atoms. (The more closely packed the atoms are the stronger the bond is and the higher the melting point.)