Chapter 6BTypes of Bonding Covalent Bonds Formed between non-metals Share valence electrons to make an octet (8) Can share 1, 2, 3, or 4 electrons with other atom(s) When atoms share electrons, they make a bonding
pair (the pair of electrons being shared) Covalent Bonds Where are the electrons found? Because of electrostatic force, electrons are most likely between atoms and
around the atom with a bigger nucleus Diatomic Elements List: H2, N2, O2, F2, Cl2, Br2, I2 Non-polar Formed between 2 atoms that are the same Please memorize this list
Lewis Structures Lewis Structures are 2D pictures to show bonds between atoms. Lewis Structures Lewis Structures- Guidelines
1. 2. 3. 4. 5. Only for covalent bonds e- are shared nonmetals
Each atom (usually) wants 8 valence electrons. Electrons are shared in pairs. Polyatomic molecules (3 or more atoms) have 1 (or more) central atoms. 6. Number of covalent bonds a nonmetal can have is: bonds = 8 (valence e-) Lewis Structures- Steps
1. Write the electron dot symbol for each element. Lewis Structures- Steps 2. Determine how many valence electrons are availa ble. Lewis Structures- Steps 3. Place element with the most unpaired e- in the ce
nter. Lewis Structures- Steps 4. Place the remaining elements around the central atom. Lewis Structures- Steps 5. Create as many single bonds (sharing 1 e- from ea
ch element) as possible. Lewis Structures- Steps 6. Create a second bond (and third) if necessary to g ive each 8 valence e-
Lewis Structures- Steps 7. Check by counting total number of electrons and make sure it is the same as Step #2. Lewis Structures Try these: CHCl3 SO2
Polyatomic Ions An ion which are composed of two or more atoms When certain elements are part of polyatomic mol ecule but have 1 or more missing valence electron s, can gain and become polyatomic anion or lose (polyatomic cation) Why? So every element in molecule has an octet
Cl [ Cl ] Polyatomic Ions
Example 1: OH- Polyatomic Ions Example 2: NH4+ Polyatomic Ion with -1 charge Polyatomic Ion with -2 charge
acetate - C2H3O2bicarbonate (or hydrogen carbonate) - HCO3bisulfate (or hydrogen sulfate) - HSO4hypochlorite - ClOchlorate - ClO3chlorite - ClO2cyanate - OCNcyanide - CNdihydrogen phosphate - H2PO4hydroxide - OHnitrate - NO3nitrite - NO2perchlorate - ClO4permanganate - MnO4thiocyanate - SCN- carbonate - CO32chromate - CrO42dichromate - Cr2O72hydrogen phosphate - HPO42peroxide - O22sulfate - SO42sulfite - SO32thiosulfate - S2O32Polyatomic Ion with -3 charge borate - BO33phosphate - PO43- Ionic Bonding Group 1 (like Na) has a single valenc
e electron. Ionization energy is? Small Group 17 (like Cl) needs 1 valence el ectron. Its electron affinity is? High When Na and Cl react Cl steals an electron from Na
Then creates an ionic bond & ionic comp ound Ionic Compounds Particles in ionic compounds are charged, but sum of all charges = 0, so- electrically neutral Ratio of cations to anions needed for electric neutr al decides the chemical formula (formula unit)
Na gives 1 e- to Cl Na+, Cl Ratio: 1 Na+: 1 Cl- or NaCl Ionic Compounds Example: What about Ca and F? How many e- does Ca have? F? Ionic Compounds
Ions in ionic compound usually arrange themselve s into tight and pretty crystal shapes This is called a crystal lattice Types of Chemical Bonds 3rd type Metallic Bond Atoms with weak electron affinity that easily share their
valence electrons (usually metals) Metallic Bonding Most metals need 6+ electrons to fill valence shell Plus holes in the d and f orbitals And low electron affinities Metals form metallic bonds by sharing
electrons a LOT of electrons Electron-sea theory (free electron theory) Crystal lattice of metal atoms in a sea of moving electrons Metallic Bonding Metals have low ionization energy, so they freely l ose an electron to share and become cations
These delocalized electrons are the glue for keepin g the cations (metal atoms) together Overview Bonds and Their Properties Elements that Bond
Valence Electrons Type of bond Bond polarity
nonmetal/ nonmetal Tightly shared Covalent
Low to medium metal/ nonmetal Transferred
Ionic High metal/ metal
Widely shared Metallic ----
