2Chemical Bonding is the mutual electrical attraction between the nuclei and valence electrons of different atoms that binds the atoms together.
3chemical formula.The composition of a formula is given by its chemical formula.A chemical formula indicates the relative number of atoms combined using atomic symbols and numeric subscriptsH2O, C6H12O8, FeCl3, CaS, Li3P
4Diatomic molecules Di = two Atomic = atoms two atoms Diatomic molecules contain only two atoms.F2H2NaCl
5Learn the following diatomic elements Cl2Br2I2At2H2O2N2HalHONAll the hologens plus Hydrogen, Oxygen and Nitrogen
6Lewis Structures Lewis Structures only show the valence electrons. Write the element symbolC
7Lewis StructuresPlace one dot to the right of the symbolC
8Lewis StructuresThen add the next electron below the symbolC
9Lewis StructuresThe next electron goes to the leftC
10Lewis StructuresContinue moving around the symbol until all electrons have been added. N
11Lewis StructuresUsing electron dot diagrams, a diatomic molecule of hydrogen can be represented asH HB period ¼
12Write the Lewis Structures for the following elements Li Be B CN O F Ne
13Lewis Structures are useful in seeing where an atom is willing to make a bond Atoms can not bond when electrons are paired
14Helium has full shell with two electrons So it is written
15N has 5 valence electrons N:It can only bond in three spots
16Chemical Bonding There are several types of bonds – Ionic Covalent Metallic
17Covalent bondsCovalent bonds are when nonmetallic elements share an electron pair.Nm Nm
18This can be two hydrogen atoms, H2 or many different elements such as in sucrose (C6H12O6)
19Molecular compoundMolecular compound is the simplest unit for molecules.Remember that only the valance electron are involved in bonding.A molecule is a neutral group of atoms that are held together by covalent bonds.Atoms share electrons
20Covalent bonds are when nonmetallic elements share an electron pair. Nm Nm1s 2s pF .F .F FF F This is the octet rule for covalent bonding.
21There are several types of covalent bonds. PolarNonpolarCoordinateThey tell how well elements share electrons
22Polar Covalentis a covalent bond that does not share the electrons equally.One side is slightly + and the other is slightly –Because there are two poles of charge involve, the bond is a dipole.H O
23A dipole caused by the polar covalent bond of the water molecule
24Nonpolar Covalentis a covalent bond where the electrons are evenly shared.F F
25Electronegativity! So how do we know what type of bond we have? CovalentNonpolar Polar IonicE %
26Sulfur’s electronegativity is 2.5 Hydrogen’s electronegativity is 2.1 Use the electronegative difference to determine the bond type. The electronegativity can be found on the periodic tableSulfur and HydrogenSulfur’s electronegativity is 2.5Hydrogen’s electronegativity is 2.1S – H = = 0.4Where does it fall?Polar covalent
27Which element is least negative? So it is written first in the formula
28Try some more F2 or F – F, SF4, LiF Compound F2 SF4 LiF Electronegativity DifferenceType of Bond
29The HF (Hydrofluoric) can be written: + - + -H – F HFThe '+' and '-' symbols indicate partial positive and negative charges.
30Coordinate covalentbond is a bond formed when one atom provides both electrons in a shared pair.H N HH
31How do we know if a double or triple bond in needed? Using the equations to correctly draw the Lewis Structure and Structural Formula for each of the following.All Single Bonds6(N) + 2 = VEN= number of atoms (not counting H)VE = # of valence electrons
35Network Solids"Covalent Crystals" (crystal is used to describe Ionic structures) (Diamonds)HardGood insulatorsTransparentHigh Melting Point
36Properties of Covalent Compounds These are poor conductors of electricity in the fused or dissolved stateNonelectrolytes-do not conduct electricity in waterPoor conductors of heat and electricityBrittle or cleave rather than deform
37Covalent Compounds Exist as neutral molecules (C6H12O2) Solids, liquids, or gases (C6H12O2(s), H2O(l), CO2(g))Lower melting and boiling points (i.e., often exist as a liquid or gas at room temperature)
38Covalent CompoundsRelatively weak force of attraction between moleculesRemain as same molecule in water and will not conduct electricityH2O(l),C6H12O2(s) → C6H12O2(aq)
39Naming Covalent Compounds All covalent compounds have two word names. The first word is the first element in the formula and the second corresponds to the second element in the formula except that "-ide" is substituted for the end.
40Rules for Naming Binary Covalent Compounds A binary covalent compound is composed of two different nonmetal elements. For example, a molecule of chlorine trifluoride, ClF3 contains 1 atom of chlorine and 3 atoms of fluorine.
41Rules for Naming Binary Covalent Compounds Rule 2. The second element in the name is named as if it were an anion, i.e., by adding the suffix -ide to the name of the element.
42Rules for Naming Binary Covalent Compounds Rule 3. If both elements are in the same group, the element with the bigger period number is written first in the name. So , BrF is named “bromine fluoride", because bromine is the first element and fluorine is the second element.
43Rules for Naming Binary Covalent Compounds Rule 4. Greek prefixes are used to indicate the number of atoms of each nonmetal element in the chemical formula for the compound.Exception: The only time “mono” is used is with oxygen
44Naming Covalent Compounds If there is more than one atom of an element in a molecule, we need to add prefixes to these words to tell us how many are present. Here are the prefixes you'll need to remember:
45mono- (use only for oxygen) Prefixes for CovalentNumber of atomsPrefix1mono- (use only for oxygen)2di-3tri-4tetra-5penta-6hexa-7hepta-8octa-9Nona-10Deca-
46Naming Practice SH2 P2S3 C4F10 NO sulfur dihydride diphosphorous trisulfidetetracarbondecafluoridenitrogenmonoxide
47Some important exceptions To the naming scheme occur because the compounds were originally named before the methodical naming scheme above became widespread. Nowadays, these names are so common that they're officially recognized:H2O is "water"NH3 is "ammonia"CH4 is "methane"