Ch 6
Sec 6.1 Atoms seldom exist as independent particles in nature. Almost everything is a combination of atoms that are held together by a chemical bond. A chemical bond is a mutually electrical attraction between the nuclei and valence e - of different atoms. 3 types of chemical bonds: 1. Ionic 2. Covalent 3. Metallic
Ionic - electrical attraction between large # s of cations and anions. Transfer of e - from a metal to a non-metal. Covalent the two atoms share the e -. Normally between non-metal and non-metals. Metallic the chemical bonding that results from the attraction between metal atoms and the surrounding sea of e -. (Show overheads)
Electronegativity chart pg 151 Difference in Electronegativity = Polarity (overhead) Non-polar bond the e - is shared equally. Polar bond the e - is shared unequally. One atom attracts the e - stronger. We say the atom that attracts the e - more is the more negative atom.
Ex. Classify the bonds of each of the following elements with Sulfur. Which atom is more negative? Bonding between S and: Electronegativity Difference Bond Type More neg. atom Na H Cs Cl S For most general purposes: metal + non-metal = ionic bond non-metal + non-metal = covalent bond
ex. Compound Electronegativity Difference Bond Type More Negative atom H 2 NaCl H 2 O
Sec. 6-2 A molecule is a neutral group of atoms that are held together by covalent bonds (sharing). i.e. must be a non-metal and a non-metal Molecular compound a chemical compound whose simplest units are molecules. ex. Water, sugar, etc. Molecular formula shows the types and # of atoms combined in a single molecule of a molecular compound. ex. H 2 O has 2 H and 1 O
Diatomic molecule can form a molecule when bonded with itself. It must contain 2 atoms. H, N, O, F, Cl, Br, I can form diatomic molecules. (They form a 7 and there are 7 of them) By sharing e - in overlapping orbital's, each H atom in the H 2 molecule experiences the effect of a stable 1s 2 electron configuration. (show orbital s)
Ex. F 2 Ex. HF
Electron dot notation electron configuration that only uses valence e - and uses dots to represent e -. # of valence e - Electron dot notation examples
Write the electron dot notation for : 1. P 2. Si 3. S 4. Cl 5. Xe
Lewis Structures electron dot notation can also be used to represent molecules. Ex. H 2 Ex. F 2 Ex. Cl 2
Structural Formula just shows the bond, not the unshared e -. ex. H 2 O Draw the Lewis Structures and Structural Formula for: Molecular Formula Lewis Structure Structural Formula NH 3 H 2 S CH 3 I
Double and Triple bonds needed when there is not enough valence electrons to go around. Molecular Form Structural Formula C 2 H 4 CH 2 O CO 2 N 2 O 3 O 3 show resonance which shows multiple Lewis dot structures.
Sec 6-3 Most of the rocks and minerals that make up the Earth s crust consists of (+) and (-) ions held together by ionic bonding. An ionic compound transfers electron so that the compound becomes neutral. Metal + non-metal = ionic bonding (Overhead)
Ionic bond will shatter when hammered. As a layer is shifted toward the next, like charges are beside each other causing them to repel and shatter. Bond energy energy needed to break 1 bond between 2 atoms. ** Overall, ionic bonds are stronger than covalent bonds. Polyatomic Ions a charged group of covalently bonded atoms. Know this list!!
Sec 6-4 Metallic bonding the chemical bonding that results from the attraction between metal atoms and the surrounding sea of e -. (Overhead) 1. The luster of metals is caused by the emission of photos when the excited electron returns to ground state. 2. This sea of electrons allows for the conductivity of heat and electricity. 3. Metals are malleable and ductile because the metallic bonding is the same in all directions throughout the solid. One plane of atoms can slide past another with out resistance.
1. Type of elements involved. Metallic Ionic Covalent 2. What happens to the electrons? 3. Conductivity 4. Physical State at room temperature. 5. Bond Strength 6. Other Characteristics.
Sec 6-5 Board notes